ARM: s3c: include header for prototype of s3c2410_modify_misccr

Include the header with prototype of s3c2410_modify_misccr to fix W=1
warning:

  arch/arm/mach-s3c/gpio-samsung.c:1309:14: warning:
    no previous prototype for ‘s3c2410_modify_misccr’ [-Wmissing-prototypes]

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20211111091123.50853-1-krzysztof.kozlowski@canonical.com