mmc: sdhci-pxav3: Add base clock quirk

Enable the quirk SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN since
SD_CAPABILITIES_1[15:8](BASE_FREQ) can't get correct base clock value.
It returns a fixed pre-set value like 200 on some sdhci-pxav3 based
platforms like MMP3 while return 0 on the other sdhci-pxav3 based
platforms.  So we enable the quirk and get the base clock via function
get_max_clock. Also add get_max_clock.

Reported-by: Philip Rakity <prakity@marvell.com>
Reviewed-by: Philip Rakity <prakity@Marvell.com>
Acked-by: Zhangfei Gao <zhangfei.gao@marvell.com>
Signed-off-by: Kevin Liu <kliu5@marvell.com>
Signed-off-by: Chris Ball <cjb@laptop.org>