ARM: qcom: Increase MMC_BLOCK_MINORS in defconfig

There are currently more than 16 partitions on the eMMC of all recent
Qualcomm devices. Increase the number of minors per block device to
detect all available partitions.

Signed-off-by: Georgi Djakov <gdjakov@mm-sol.com>
Signed-off-by: Kumar Gala <galak@codeaurora.org>