clk: clk-gate-shared: fix "no previous prototype" warning ...

The patch fixes these compiler's warnings:

  drivers/clk/clk-gate-shared.c:72:13: warning: no previous prototype for 'clk_gate_shared_alloc' [-Wmissing-prototypes]
   struct clk *clk_gate_shared_alloc(const char *name, const char *parent, const char *companion,
               ^
  drivers/clk/clk-gate-shared.c:89:6: warning: no previous prototype for 'clk_gate_shared_free' [-Wmissing-prototypes]
   void clk_gate_shared_free(struct clk *clk)
        ^

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

clk: Add support for shared gates ...

Sometimes a single software control knob controls multiple gates
in hardware. This patch adds support for shared gates which help
coping this situation. The first gate is registered with the hardware
gate as usual, the others are registered as shared gates which does
not have hardware control itself, but only switches the real hardware
gate.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>