pinctrl: msm: Simplify msm_config_reg() and callers

We don't need to check for a negative reg here because reg is
always the same and is always non-negative. Also, collapse the
switch statement down for the duplicate cases.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>