powerpc: fix 8xx and 6xx final link failures

powerpc: fix 8xx and 6xx final link failures

As of commit b81f18e55e9f4ea81759bcb00fea295de679bbe8 ("powerpc/boot:
Only build board support files when required.") the two defconfigs
ep88xc_defconfig and storcenter_defconfig would fail final link as
follows:

  WRAP    arch/powerpc/boot/dtbImage.ep88xc
arch/powerpc/boot/wrapper.a(mpc8xx.o): In function `mpc885_get_clock':
arch/powerpc/boot/mpc8xx.c:30: undefined reference to `fsl_get_immr'
make[1]: *** [arch/powerpc/boot/dtbImage.ep88xc] Error 1

 ...and...

  WRAP    arch/powerpc/boot/cuImage.storcenter
arch/powerpc/boot/cuboot-pq2.o: In function `pq2_platform_fixups':
cuboot-pq2.c:(.text+0x324): undefined reference to `fsl_get_immr'
make[1]: *** [arch/powerpc/boot/cuImage.storcenter] Error 1

We need the fsl-soc board files built for these two platforms.

Cc: Tony Breeds <tony@bakeyournoodle.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Fixes: b81f18e55e9f ("powerpc/boot: Only build board support files when required.")
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>