mmc: core: Revert "skip card initialization if power class selection fails"

This reverts commit 3d93576e(skip card initialization if
power class selection fails).
Problem has been reported when this is used with eMMC4.41
card with Tegra Platform. Till the issue is root caused,
bus width selection failure should not be treated as fatal.

Reported-by: Marc Dietrich <marvin24@gmx.de>
Signed-Off-by: Venkatraman S <svenkatr@ti.com>
CC: Ulf Hansson <ulf.hansson@stericsson.com>
CC: Subhash Jadavani <subhashj@codeaurora.org>
CC: Saugata Das <saugata.das@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>