mmc: core: Rename ->reset() bus ops to ->hw_reset()

The bus ops ->reset() executes a full HW reset of the card, as the calling
function mmc_hw_reset() also indicates by its name. Let's convert to follow
the similar names, for both the bus ops callback and for the corresponding
bus ops functions, as to clarify the purpose of code.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Quentin Schulz <quentin.schulz@bootlin.com>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>