tests/sprintf: FP tests independent of endian
tests/sprintf: FP tests independent of endian

The test access double variables as individual uint32_t. This
commit ensures that the correct uint32_t is accessed, based on
CONFIG_BIG_ENDIAN.

Signed-off-by: Martin Åberg <37424e7fbe3f8590d57db5ed6ae5b8866742b6be@gaisler.com>

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