tests/kernel/sleep: relax upper bound for TI CC13X2/CC26X2 RTC
tests/kernel/sleep: relax upper bound for TI CC13X2/CC26X2 RTC

The RTC on TI CC13X2/CC26X2 is a 32 KHz clock for which the minimum
compare delay is 3 ticks. When using it as the system clock, we need
to relax the upper bound to ensure the test succeeds.

Signed-off-by: Vincent Wan <0da4a49376daf88459b96a63301ecd5aff2f3b80@linaro.org>

finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,nashif/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr