ARM: s3c24xx: Fix typo in guard macro of s3c2412.h

The guard macro __ARCH_ARM_REGS_S3C24XX_S3C2412_H in header s3c2412.h
doesn't match the #ifndef macro __ARCH_ARM_MACH_S3C24XX_S3C2412_H.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>