mmc: Read eMMC partition access bits before card reset

eMMC specification in section "Access partitions" says that all reset
events will restore the access bits in PARTITION_CONFIG CSD register to
default User Data Area value (0b000).

So read partition access bits from PARTITION_CONFIG CSD register before
issuing card reset. This allows SPL/U-Boot to get information which eMMC
partition was in use before SPL/U-Boot was booted. For some platforms this
is the way how to determinate boot partition from which BootROM loaded SPL.

Signed-off-by: Pali Rohár <pali@kernel.org>