tests: kernel: fp_sharing: minor fix in #ifdef expression
tests: kernel: fp_sharing: minor fix in #ifdef expression

We need to use the ARMV7_M_ARMV8_M_FP Kconfig symbol,
which denotes the Floating-Point capabilities, instead
of the option that signifies the Cortex-M variant. Fix
is of minor importance, as long as the #ifdef block
remains empty.

Signed-off-by: Ioannis Glaropoulos <5921cc8bab7e1d4329f52fd8f6268f9692e3de80@nordicsemi.no>

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