clk: emev2: Silence sparse warnings

drivers/clk/shmobile/clk-emev2.c:37:14: warning: symbol 'smu_base' was not declared. Should it be static?

Cc: Takashi Yoshii <takasi-y@ops.dti.ne.jp>
Cc: Magnus Damm <damm@opensource.se>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>