mmc: block: Remove call to mmc_blk_set_blksize

It no longer exists.

CRs-Fixed: 561382
Change-Id: I1ca5e8f93241264ed9ffdce53067cb16476c1c66
Signed-off-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>