arm64: fix return value type of memcpy_mcs()

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6AQE8
CVE: NA

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The return value type of function memcpy_mcs() should be unsigned long.
Currently, using this function will force type conversion, but the error
of the return value type must be corrected.

Fixes: 7aaf7c57 ("arm64: introduce copy_mc_to_kernel() implementation")
Signed-off-by: NTong Tiangen <tongtiangen@huawei.com>

arch/arm64/include/asm/string.h

@@ -36,8 +36,8 @@ extern void *memcpy(void *, const void *, __kernel_size_t);
 extern void *__memcpy(void *, const void *, __kernel_size_t);
 
 #define __HAVE_ARCH_MEMCPY_MC
-extern unsigned long *memcpy_mcs(void *, const void *, __kernel_size_t);
-extern unsigned long *__memcpy_mcs(void *, const void *, __kernel_size_t);
+extern unsigned long memcpy_mcs(void *, const void *, __kernel_size_t);
+extern unsigned long __memcpy_mcs(void *, const void *, __kernel_size_t);
 
 #define __HAVE_ARCH_MEMMOVE
 extern void *memmove(void *, const void *, __kernel_size_t);