mmc: Skip changing bus width for MMC cards earlier than version 4.0

Wider bus widths (larger than default 1 bit) appeared in MMC standard
version 4.0. So, for MMC cards of any earlier version trying to change
the bus width (including ext_csd comparison) does not make any sense.
It may work incorrectly and at least cause unnecessary timeouts.
So, just skip the entire bus width related activity for earlier versions.

Signed-off-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Tested-by: Alexey Brodkin <abrodkin@synopsys.com>