EDAC: Handle return value of kasprintf()

kasprintf() can fail and we must check its return value.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Cc: linux-edac@vger.kernel.org
[ Merged into a single patch, small formatting fixups. ]
Signed-off-by: Borislav Petkov <bp@suse.de>