mmc: dw_mmc-socfpga: Remove redundant of_match_ptr

'dw_mci_socfpga_match' is always compiled in.
Hence of_match_ptr is not necessary.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>