asm-generic: COMMON_CLK defines __clk_{get,put}

If CONFIG_COMMON_CLK is selected then __clk_get and __clk_put are
defined in drivers/clk/clk.c and declared in include/linux/clkdev.h.

Sylwester's series[0] to properly support clk_{get,put} in the common
clock framework made changes to the asm-specific clkdev.h headers, but
not the asm-generic version. Tomeu's recent changes[1] to introduce a
provider/consumer split in the clock framework uncovered this problem,
causing the following build error on any architecture using the
asm-generic clkdev.h (e.g. x86 architecture and the ACPI LPSS driver):

In file included from drivers/acpi/acpi_lpss.c:15:0:
include/linux/clkdev.h:59:5: error: conflicting types for ‘__clk_get’
 int __clk_get(struct clk_core *clk);
     ^
In file included from arch/x86/include/generated/asm/clkdev.h:1:0,
                 from include/linux/clkdev.h:15,
                 from drivers/acpi/acpi_lpss.c:15:
include/asm-generic/clkdev.h:20:19: note: previous definition of ‘__clk_get’ was here
 static inline int __clk_get(struct clk *clk) { return 1; }
                   ^

Fixed by only declarating  __clk_get and __clk_put when
CONFIG_COMMON_CLK is set.

[0] http://lkml.kernel.org/r/<1386177127-2894-5-git-send-email-s.nawrocki@samsung.com>
[1] http://lkml.kernel.org/r/<1409758148-20104-1-git-send-email-tomeu.vizoso@collabora.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

include/asm-generic/clkdev.h

@@ -15,10 +15,12 @@
 
 #include <linux/slab.h>
 
+#ifndef CONFIG_COMMON_CLK
 struct clk;
 
 static inline int __clk_get(struct clk *clk) { return 1; }
 static inline void __clk_put(struct clk *clk) { }
+#endif
 
 static inline struct clk_lookup_alloc *__clkdev_alloc(size_t size)
 {