staging: ion: Add HAVE_MEMBLOCK config dependency

The kbuild test robot reported a build issue w/ ION on m68k:

drivers/staging/android/ion/ion.c: In function 'ion_reserve':
drivers/staging/android/ion/ion.c:1526:4: error: implicit declaration of function 'memblock_alloc_base' [-Werror=implicit-function-declaration]
drivers/staging/android/ion/ion.c:1528:11: error: 'MEMBLOCK_ALLOC_ANYWHERE' undeclared (first use in this function)
drivers/staging/android/ion/ion.c:1528:11: note: each undeclared identifier is reported only once for each function it appears in
drivers/staging/android/ion/ion.c:1537:4: error: implicit declaration of function 'memblock_reserve' [-Werror=implicit-function-declaration]
   cc1: some warnings being treated as errors

This is caused by ION using memblock functionality which m68k doesn't support.

This patch adds a HAVE_MEMBLOCK dependency to the ION config.

Acked-by: Colin Cross <ccross@android.com>
Cc: Android Kernel Team <kernel-team@android.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>