powerpc/8xx: Remove empty asm/mpc8xx.h

m8xx_pcmcia_ops was the only thing in this file (other than a comment
that describes a usage that doesn't match the file's contents); now
that m8xx_pcmcia_ops is gone, remove the empty file.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Cc: Pantelis Antoniou <pantelis.antoniou@gmail.com>
Cc: Vitaly Bordug <vitb@kernel.crashing.org>
Cc: netdev@vger.kernel.org