mmc: Avoid buffer overrun in mmc_startup()

If the CSD register contains a reserved value (4 - 7) in bits 0:2 of the
TRAN_SPEED field, a buffer overrun occurs. Resize the mapping table.

According to the original report
https://lore.kernel.org/u-boot/20180826231332.2491-11-erosca@de.adit-jv.com/


reserved values have been observed resulting in a buffer overrun.

Reported-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Fixes: 272cc70b ("Add MMC Framework")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>