C6X: deal with memblock API changes

Recent memblock related commits require the following C6X changes:

  * commit 24aa0788
    asm/memblock.h no longer required

  * commit 1440c4e2
    memblock_analyze() no longer needed to update total size

  * commit fe091c20
    memblock_init() no longer needed

Signed-off-by: Mark Salter <msalter@redhat.com>