staging: delete all duplicated endian crap from rtl8712 driver

This driver had headers like big_endian.h, little_endian.h, swab.h
and yet we can throw them all in the trash can and the thing
still builds on x86-64 and ppc, just by deleting the references
to the deleted files.

Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>