Use polled waiting on platforms that support it

Due to context switching overhead waiting a very short amount of time on
a sleeping thread is often not accurate and in fact not usable for timing
critical usage i.e. in a driver. Thus we use polled waiting for ranges
in the us range on platforms that support it instead. The fallback is
the thread sleeping mechanism.

This includes:

* ARM platforms with CYCCNT register (ARMv7, ARMv8) this is
  incremented at CPU clock frequency
* GD32VF103 RISC-V port with CSR_MCYCLE register this is incremented at
  CPU clock frequency
* RP2040 ARMv6 port which uses the integrated timer peripheral which is
  incremented with a fixed 1MHz frequency

platforms/chibios/_wait.h

@@ -30,6 +30,11 @@
 
 #ifdef WAIT_US_TIMER
 void wait_us(uint16_t duration);
+#elif PORT_SUPPORTS_RT == TRUE
+#    define wait_us(us)                                            \
+        do {                                                       \
+            chSysPolledDelayX(US2RTC(REALTIME_COUNTER_CLOCK, us)); \
+        } while (0)
 #else
 #    define wait_us(us)                     \
         do {                                \

platforms/chibios/chibios_config.h

@@ -21,6 +21,9 @@
 
 #if defined(MCU_RP)
 #    define CPU_CLOCK RP_CORE_CLK
+// ChibiOS uses the RP2040 timer peripheral as its real time counter, this timer
+// is monotonic and running at 1MHz.
+#    define REALTIME_COUNTER_CLOCK 1000000
 
 #    define USE_GPIOV1
 #    define PAL_OUTPUT_TYPE_OPENDRAIN _Static_assert(0, "RP2040 has no Open Drain GPIO configuration, setting this is not possible");
@@ -102,10 +105,19 @@
 #    endif
 #endif
 
+#if defined(MCU_MIMXRT1062)
+#    include "clock_config.h"
+#    define CPU_CLOCK BOARD_BOOTCLOCKRUN_CORE_CLOCK
+#endif
+
 #if defined(HT32)
 #    define CPU_CLOCK HT32_CK_SYS_FREQUENCY
 #    define PAL_MODE_ALTERNATE PAL_HT32_MODE_AF
 #    define PAL_OUTPUT_TYPE_OPENDRAIN (PAL_HT32_MODE_OD | PAL_HT32_MODE_DIR)
 #    define PAL_OUTPUT_TYPE_PUSHPULL PAL_HT32_MODE_DIR
 #    define PAL_OUTPUT_SPEED_HIGHEST 0
 #endif
+
+#if !defined(REALTIME_COUNTER_CLOCK)
+#    define REALTIME_COUNTER_CLOCK CPU_CLOCK
+#endif