arch/arm/imx9: clockconfig: preparatory cleanup for i.MX93 support.

- Guard imx9_gpc.h inclusion with CONFIG_IMX9_WFI_AWAKES_AT_SYSTICK
  to avoid a GPC dependency on chips that lack GPC
- Add depends on ARCH_CHIP_IMX95_M7 to IMX9_WFI_AWAKES_AT_SYSTICK
  since GPC wake configuration is i.MX95-specific
- Move XTAL_FREQ and ROOT_CLOCK_OFFSET defines to imx95_clock.h
- Make imx9_sm_setrootclock() and imx9_sm_getipfreq() static;
  they are not referenced outside this translation unit

Signed-off-by: Maarten Zanders <maarten@zanders.be>

arch/arm/src/imx9/Kconfig

@@ -49,6 +49,7 @@ endif
 config IMX9_WFI_AWAKES_AT_SYSTICK
 	bool "WFI awakes at systick interrupts"
 	default y
+	depends on ARCH_CHIP_IMX95_M7
 	---help---
 	Configure the GPC to wake up from systick interrupts at WFI
 	instruction

arch/arm/src/imx9/hardware/imx95/imx95_clock.h

@@ -37,6 +37,9 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
+#define XTAL_FREQ 24000000u
+#define ROOT_CLOCK_OFFSET 41
+
 typedef enum
 {
     EXT_CLK  = 0,

arch/arm/src/imx9/imx9_clockconfig.c

@@ -37,7 +37,11 @@
 #include <arch/barriers.h>
 
 #include "arm_internal.h"
+
+#ifdef CONFIG_IMX9_WFI_AWAKES_AT_SYSTICK
 #include "hardware/imx9_gpc.h"
+#endif
+
 #include "imx9_clockconfig.h"
 #include "imx9_scmi.h"
 
@@ -45,12 +49,6 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-/* The base oscillator frequency is 24MHz */
-
-#define XTAL_FREQ 24000000u
-
-#define ROOT_CLOCK_OFFSET 41
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -87,7 +85,7 @@ void imx9_clockconfig(void)
 }
 
 #ifdef CONFIG_IMX9_CLK_OVER_SCMI
-int imx9_sm_setrootclock(sm_clock_t *sm_clk)
+static int imx9_sm_setrootclock(sm_clock_t *sm_clk)
 {
   scmi_clock_rate_t rate = /* clang-format off */
     {
@@ -156,7 +154,7 @@ int imx9_sm_setrootclock(sm_clock_t *sm_clk)
   return OK;
 }
 
-int imx9_sm_getipfreq(sm_clock_t *sm_clk)
+static int imx9_sm_getipfreq(sm_clock_t *sm_clk)
 {
   scmi_clock_rate_t rate = /* clang-format off */
     {