gpio: 74xx-mmio: Use bits instead of plain numbers for flags

The initial code was misleading to use bitwise AND against plain number,
and the commit d3054ba1 ("gpio: 74xx-mmio: Check MMIO_74XX_DIR_IN flag
in mmio_74xx_dir_in()") missed that. Switch definitions to be defined bits
for the correct comparison.

Fixes: d3054ba1 ("gpio: 74xx-mmio: Check MMIO_74XX_DIR_IN flag in mmio_74xx_dir_in()")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>