CLK: SPEAr: make aux_clk_masks structures const

Make these const as they are either stored in the masks 'const' field
of a clk_aux structure or passed to the function clk_register_aux
having the argument as const.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>