x86/mce/dev-mcelog: Fix -Wstringop-truncation warning about strncpy()

The kbuild test robot reported this warning:

  arch/x86/kernel/cpu/mce/dev-mcelog.c: In function 'dev_mcelog_init_device':
  arch/x86/kernel/cpu/mce/dev-mcelog.c:346:2: warning: 'strncpy' output \
    truncated before terminating nul copying 12 bytes from a string of the \
    same length [-Wstringop-truncation]

This is accurate, but I don't care that the trailing NUL character isn't
copied. The string being copied is just a magic number signature so that
crash dump tools can be sure they are decoding the right blob of memory.

Use memcpy() instead of strncpy().

Fixes: d8ecca4 ("x86/mce/dev-mcelog: Dynamically allocate space for machine check records")
Reported-by: kbuild test robot <[email protected]>
Signed-off-by: Tony Luck <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: aegl

arch/x86/kernel/cpu/mce/dev-mcelog.c

@@ -349,7 +349,7 @@ static __init int dev_mcelog_init_device(void)
 	if (!mcelog)
 		return -ENOMEM;
 
-	strncpy(mcelog->signature, MCE_LOG_SIGNATURE, sizeof(mcelog->signature));
+	memcpy(mcelog->signature, MCE_LOG_SIGNATURE, sizeof(mcelog->signature));
 	mcelog->len = mce_log_len;
 	mcelog->recordlen = sizeof(struct mce);