tests filesystem.fat.api: Do not run on native_posix_64

The FAT FS code clearly does not support platforms where
long is 64bits. See
https://github.com/zephyrproject-rtos/fatfs/blob/master/include/integer.h#L30

So, do not try to run it in native_posix_64
Fixes #21536
Fixes #19231

Signed-off-by: Alberto Escolar Piedras <alpi@oticon.com>
1 file changed