mmc: sdhci-msm: Store clock scaling frequencies in a dedicated table

Use a separate table to store the platform specific clock-scaling
frequencies.

The generic table where these frequencies used to be stored, would
get updated (in some cases) during clock scaling initialization.
But when a new card is inserted (In the case of a removable card),
the frequencies supported by the card should be compared against the
platform specific frequencies.

By storing these values in a separate table, these values would
remain intact and this table can be used for initializing the
generic table during clock-scaling initialization.

Change-Id: I5729f18a975f849bc2965a946473a9cdbd81e94a
Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>