mmc: core: eMMC signal voltage does not use CMD11

eMMC chips do not use CMD11 when changing voltage.  Add extra
argument to call to indicate if CMD11 needs to be sent.

Signed-off-by: Philip Rakity <prakity@marvell.com>
Reviewed-by: Arindam Nath <arindam.nath@amd.com>
Signed-off-by: Chris Ball <cjb@laptop.org>