gpio/microblaze: Eliminate duplication of of_get_named_gpio_flags()

of_reset_gpio_handle() is largely a cut-and-paste copy of
of_get_named_gpio_flags(). There really isn't any reason for the
split, so this patch deletes the duplicate function

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Michal Simek <monstr@monstr.eu>