powerpc/85xx: Abstract common define of signal multiplex control for qe

The mpc85xx_rdb and mpc85xx_mds have commom define of signal multiplex for qe, so
they need to go in common header, the patch abstract them to fsl_guts.h

Signed-off-by: Zhicheng Fan <b32736@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>