wireless/cc1101: Make SPI burst and single frequencies configurable

This patch introduces CONFIG_CC1101_SPIFREQ_BURST and
CONFIG_CC1101_SPIFREQ_SINGLE to Kconfig, allowing users to override
the default SPI frequencies for the CC1101 wireless driver.

Previously, these values were hardcoded to 6.5 MHz and 9.0 MHz
respectively. While these are safe defaults for many setups, specific
hardware designs, high routing capacitance, or platforms utilizing
internal GPIO switching matrices (such as the ESP32) can suffer from
signal integrity degradation at these speeds. By exposing these to
Kconfig, users can easily adjust the clock speeds to match their
hardware capabilities without modifying the core driver source.

Impact:
- Build: Adds two new Kconfig options under WL_CC1101.
- Runtime: Retains 6.5 MHz / 9.0 MHz defaults. Behavior only changes
  if overridden via menuconfig.

Testing:
- Built with default values and custom Kconfig overrides.
- Hardware Testing: Tested on a sub-optimal platform utilizing an
  internal GPIO matrix (ESP32). The CC1101 failed to load at the
  default 6.5/9.0 MHz due to signal integrity issues. Downclocking
  the frequencies to 4.0 MHz via Kconfig successfully restored
  signal integrity and allowed the driver to initialize and operate
  normally.

Signed-off-by: Chip L. <chplee@gmail.com>

drivers/wireless/Kconfig

@@ -26,6 +26,18 @@ config CC1101_SPIDEV
 		Selects the SPI bus number identifying that SPI interface that
 		connects the CC1101 to the MCU.
 
+config CC1101_SPIFREQ_BURST
+	int "SPI burst frequency"
+	default 6500000
+	---help---
+		SPI burst frequency (Hz, no delay) for CC1101.
+
+config CC1101_SPIFREQ_SINGLE
+	int "SPI single access frequency"
+	default 9000000
+	---help---
+		SPI single access frequency (Hz, single access only - no delay) for CC1101.
+
 endif
 
 config WL_CC1101_IGNORE_VERSION

drivers/wireless/cc1101.c

@@ -109,8 +109,16 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define CC1101_SPIFREQ_BURST    6500000 /* Hz, no delay */
-#define CC1101_SPIFREQ_SINGLE   9000000 /* Hz, single access only - no delay */
+#ifndef CONFIG_CC1101_SPIFREQ_BURST
+#  define CONFIG_CC1101_SPIFREQ_BURST    6500000 /* Hz, no delay */
+#endif
+
+#ifndef CONFIG_CC1101_SPIFREQ_SINGLE
+#  define CONFIG_CC1101_SPIFREQ_SINGLE   9000000 /* Hz, single access only - no delay */
+#endif
+
+#define CC1101_SPIFREQ_BURST    CONFIG_CC1101_SPIFREQ_BURST
+#define CC1101_SPIFREQ_SINGLE   CONFIG_CC1101_SPIFREQ_SINGLE
 
 #define CC1101_MCSM0_VALUE      0x1c