mmc: tmio: give read32/write32 functions more descriptive names

mmc: tmio: give read32/write32 functions more descriptive names

Looking at the backlogs, I am not the only one who missed that the above
functions do not read u32 from one register, but create a virtual u32
from reading to adjacent u16 registers (which depending on 'bus_shift'
can be up to 8 byte apart). Because this driver supports old hardware
for which we don't have documentation, I first wrongly assumed there was
a variant which had a few u32 registers. Let's give the functions more
descriptive names to make it more obvious what is happening.

Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>