mmc: dw_mmc: Replace fifoth_val property with fifo-depth

mmc: dw_mmc: Replace fifoth_val property with fifo-depth

Replace fifoth_val property with its fifo-depth counterpart in all DW
MMC drivers. fifo-depth is a common property used in upstream Linux
kernel. The FIFOTH register value will be calculated using fifo-depth
value in DW MMC core (dw_mmc.c). This change reduces code duplication in
platform drivers, and pulls common FIFOTH register value calculation
into core dw_mmc driver where it belongs.

No functional change.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>