mmc: core: Bus width testing needs to handle suspend/resume

On reading the ext_csd for the first time (in 1 bit mode), save the
ext_csd information needed for bus width compare.

On every pass we make re-reading the ext_csd, compare the data
against the saved ext_csd data.

This fixes a regression introduced in 3.0-rc1 by 08ee80cc397ac1a3
("mmc: core: eMMC bus width may not work on all platforms"), which
incorrectly assumed we would be re-reading the ext_csd at resume-
time.

Signed-off-by: Philip Rakity <prakity@marvell.com>
Tested-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>