plat-nomadik: fix compilation warning

The compiler warns that [rf]wimsc may be used uninitialized in
this function - the warning is actually false since the uses are
in identical if()-clauses, but it can't hurt very much to read
out the values to be modified early anyway and rid the warning.

Cc: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>