UAPI: Fix arch/mips/include/asm/Kbuild to have separate header-y lines

Fix arch/mips/include/asm/Kbuild to have a separate header-y line for each
header to make them easier to relocate individually as part of the UAPI header
split.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/Kbuild

@@ -1,3 +1,5 @@
 include include/asm-generic/Kbuild.asm
 
-header-y += cachectl.h sgidefs.h sysmips.h
+header-y += cachectl.h
+header-y += sgidefs.h
+header-y += sysmips.h