mmc: sdhci-msm: Read version register properly

The version register is only 16 bits wide but we use a readl to
read it. Normally this wouldn't be a problem, but the register
offset is 0xfe, something that is not word aligned. This causes
crashes on THUMB2 kernels. Use readw instead to read the register
properly and avoid any alignment issues.

Change-Id: I3b8b14ce2f741631ef7554e3763d1d7f145077a8
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>