When using QUIRK_NONSTANDARD_CLOCK, it checks the set_clock() function
which is not used actually.  So delete it.
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>