scsi: ufs: read the device bRefClkFreq attribute

Device reference clock is a crucial parameter, as
it would fail to work in HS, if its value is different than 19.2 MHz.
This is why we should read its value upon start-up and notify
its value as a debug message.
We don't want to "blindly" configure this attribute as well, as this is
a one-time-programmable parameter and should be considered carefully
before setting it.

Change-Id: Ia2cc0f18fae1189949c30b5b2a65b763c1c46fb1
Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>