Remove sparse warning from unwind code

Running ia64 through sparse gives warnings in the unwind code.

include/asm-ia64/unwind.h:84:17: error: dubious bitfield without explicit signed' or unsigned'

Make the bitfield explicitly unsigned.

Index: linux/include/asm-ia64/unwind.h
=================================--- linux.orig/include/asm-ia64/unwind.h 2007-02-05 05:44:54.000000000 +1100
+++ linux/include/asm-ia64/unwind.h 2007-03-01 15:48:47.936874767 +1100
@@ -81,7 +81,7 @@ struct unw_frame_info {
struct unw_ireg {
unsigned long *loc;
struct unw_ireg_nat {
- long type : 3; /* enum unw_nat_type */
+ unsigned long type : 3; /* enum unw_nat_type */
signed long off : 61; /* NaT word is at loc+nat.off */
} nat;
} r4, r5, r6, r7;