mmc: sdhci_am654: Improve whitespace utilisation with regmap_*() calls

Line wrapping with the regmap_*() functions is way more conservative
than required by the 80 character rule. Expand the function calls out to
use less number of lines.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>