staging: rtl8723au: Clean up error code mess in rtw_efuse.c

Use int to return error codes, and avoid mixing and matching
true/false with _FAIL/_SUCCESS at random.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>