mmc: core: expose info about enhanced rpmb support

Following eMMC JEDEC JESD84-B51 standard, an enhanced form of
rpmb is supported. What this enhanced mode supports is in addition
to be able to write one rpmb or two rpmb frames at a time,
32 frames can be written at a time.

Expose this information present in ext csd field so that the
user space application that wants to make use of this can do so.

Signed-off-by: Krishna Konda <kkonda@codeaurora.org>
Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
Link: https://lore.kernel.org/r/1588341189-4371-1-git-send-email-vbadigan@codeaurora.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>