mmc: mxcmmc: Fix missing parentheses and brace

Looks like the adjusted syntax wasn't fully build tested. This fixes
failures with powerpc builds:

drivers/mmc/host/mxcmmc.c: In function ‘mxcmci_swap_buffers’:
drivers/mmc/host/mxcmmc.c:296:51: error: expected ‘)’ before ‘;’ token
   void *buf = kmap_atomic(sg_page(sg) + sg->offset;
                                                   ^
drivers/mmc/host/mxcmmc.c:299:1: error: expected ‘,’ or ‘;’ before ‘}’ token
 }
 ^

Fixes: b189e758 ("mmc: mxcmmc: handle highmem pages")
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>