mmc: sdhci: programmable clock calculation needs multiplier +1

According to the SD Host Controller Simplified Specification v4.20,
the multiplier value M is one more than the Clock Multiplier field.

Copied code from Linux project.  drivers/mmc/host/sdhci.c line 4405

Signed-off-by: cmachida <curtis.machida@intel.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Sean Anderson <sean.anderson@seco.com>