Wire the RTL8721F km4tz core up to a working NuttShell:
- irq.h: renumber the KM4TZ external vector table to the RTL8721F
APIRQn map (UART_LOG=24, IPC=5, +GPIOB/C, TIMER7/8, ...).
- ameba_loguart.c: fix the LOG-UART base to 0x40810000. The former
0x401C6000 belongs to a different Ameba part; the wrong base bus-
faulted on the RX interrupt-enable write while TX still worked
(LOGUART_PutChar uses its own ROM-internal base).
- ameba_app_start.c: adjust the MPU read-only / RAM regions for the
RTL8721F memory map and seed the RTC on first power-on so the
SDM32K-clocked SYSTIMER comes up (mirrors the SDK app_rtc_init).
- ameba_ipc.c: move the km4tz<->km4ns IPC to APIRQn 5 (IPC_CPU0).
- ameba_board.mk: pull in fwlib ameba_rtc.c for the RTC_* symbols.
- defconfig: RTL8721F RAM map, enable TIMER/TIMER_ARCH/ARMV8M_SYSTICK
for a live system tick, and drop the WiFi/NET stack for now.
- scripts/Make.defs: use the RTL8721F_NOR flash profile.
Boots cleanly to nsh> on hardware; tick, RX and builtin apps verified.
Signed-off-by: dechao_gong <dechao_gong@realsil.com.cn>