clk: spear: Move prototype to accessible header

clk: spear: Move prototype to accessible header

Fixes the following W=1 kernel build warning(s):

 drivers/clk/spear/spear1310_clock.c:385:13: warning: no previous prototype for ‘spear1310_clk_init’ [-Wmissing-prototypes]
 drivers/clk/spear/spear1340_clock.c:442:13: warning: no previous prototype for ‘spear1340_clk_init’ [-Wmissing-prototypes]

Cc: Viresh Kumar <vireshk@kernel.org>
Cc: Shiraz Hashim <shiraz.linux.kernel@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Rajeev Kumar <rajeev-dlh.kumar@st.com>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210126124540.3320214-20-lee.jones@linaro.org
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>