serial: s3c: Fix build of header without serial_core.h preinclusion
serial: s3c: Fix build of header without serial_core.h preinclusion

serial_s3c.h uses upf_t which is defined in serial_core.h but does not
include that itself meaning that users which include serial_s3c.h by
itself don't build.

Signed-off-by: Mark Brown <b51b9a92386687a9ac927cebfa0f978adeb8cea5@linaro.org>
[t.figa: Moved inclusion under #ifndef __ASSEMBLY__ to fix mach-exynos]
Signed-off-by: Tomasz Figa <c4885e520559c7b5b4fe1e9e188b924d2debd35e@samsung.com>
Signed-off-by: Kukjin Kim <3fc711f4e08bc570a586748633ff7c76d0e1e253@samsung.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs