mx6: clock: Add a prototype for do_mx6_showclocks()
When compiling with W=1 the following warning is observed:
arch/arm/mach-imx/mx6/clock.c:1268:5: warning: no previous prototype for ‘do_mx6_showclocks’ [-Wmissing-prototypes] int do_mx6_showclocks(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
Remove this warning by adding the function prototype into arch-mx6/clock.h file.
Signed-off-by: Diego Dorta <diego.dorta@nxp.com>
(cherry picked from commit
342b4b09b1fb58753bc46609d5ea68759b7d8626)
