fs: core: remove include of <sys/stat.h> from fs.c.
fs: core: remove include of <sys/stat.h> from fs.c.

This include is not used at all by fs.c. Zephyr includes a minimal
sys/stat.h, but only for the minimal libc.

Signed-off-by: Chris Reed <5c8e7a799cb891a0ec7887f2dd5d3bfb138b5f9c@arm.com>

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