arm: socfpga: fix up a questionable macro for SDMMC

Move the macro into the socfpga_dwmci_clksel().

Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Signed-off-by: Marek Vasut <marex@denx.de>
[fix parenthesis in the sdmmc_mask]