fix failure of mips libgcc_eh patch to apply

commit 0a16a127996cd7b5e991d47cfd8b34fd068c49b5 introduced this patch
with missing leading path component.

patches/gcc-5.2.0/0009-mipsdw.diff

@@ -1,5 +1,5 @@
---- libgcc/config/mips/linux-unwind.h.orig	2016-04-07 23:08:58.088577977 +0000
-+++ libgcc/config/mips/linux-unwind.h	2016-04-07 23:04:34.016523639 +0000
+--- a/libgcc/config/mips/linux-unwind.h	2016-04-07 23:08:58.088577977 +0000
++++ b/libgcc/config/mips/linux-unwind.h	2016-04-07 23:04:34.016523639 +0000
 @@ -27,7 +27,7 @@
     state data appropriately.  See unwind-dw2.c for the structs.  */