timing: fix ARM Cortex-M timing functions wrap-around issue

Added casts to uint32_t in arch_timing_cycles_get() to handle the
wrap-around of the 32-bit cycle counter correctly.

Signed-off-by: Simon Tomschik <simon.tomschik@askgroup.global>

arch/arm/core/cortex_m/timing.c

@@ -104,7 +104,7 @@ timing_t arch_timing_counter_get(void)
 uint64_t arch_timing_cycles_get(volatile timing_t *const start,
 				volatile timing_t *const end)
 {
-	return (*end - *start);
+	return ((uint32_t)*end - (uint32_t)*start);
 }
 
 uint64_t arch_timing_freq_get(void)