mmc: sd: Error out on bus speed switch failure

Treat bus speed switch failures as error and don't fall back on
default speed. The card status could indicate that the current
function is busy and cannot be switched. Attempt to reinit the
bus speed switch again instead of falling back to default speed.
Silently falling back to lower speed could cause performance issues.

CRs-Fixed: 849567
Change-Id: I4fcd51b82e41746620a68a0a0eb5a18d630ccbea
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>