eSDHC fails to recognize some SDHS cards, throwing timeout errors:

  mmc0: error -110 whilst initialising SD card

That's because we calculate timeout value in a wrong way: on eSDHC hosts
the timeout clock is derivied from the SD clock, which is set dynamically.

As David Vrabel suggested, deriving timeout clock from SD clock is a
common scheme, so let's implement DATA_TIMEOUT_USES_SDCLK quirk and use it
for eSDHC hosts.

Also, from now on we don't need esdhc_get_timeout_clock() callback, so
remove it.
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Cc: Pierre Ossman <pierre@ossman.eu>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: David Vrabel <david.vrabel@csr.com>
Cc: Ben Dooks <ben@fluff.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>