subsys/crc/crc_shell: Fix includes

To use the shell one does not need anymore to pull unistd.h,
if one uses sys_getopt, we need to include sys/sys_getopt.h

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

subsys/crc/crc_shell.c

@@ -8,13 +8,8 @@
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdlib.h>
-#ifdef CONFIG_NATIVE_LIBC
-#include <unistd.h>
-#else
-#include <zephyr/posix/unistd.h>
-#endif
-
 #include <zephyr/kernel.h>
+#include <zephyr/sys/sys_getopt.h>
 #include <zephyr/shell/shell.h>
 #include <zephyr/sys/crc.h>