Libunwind: Remove unused function

For build-system CFLAGS clean-up.

Bug: 18632512
Change-Id: Ib2a0a5e47ed2f8cbaf7eb4c6032f3bb18f4bbff6
diff --git a/src/arm/Gex_tables.c b/src/arm/Gex_tables.c
index 7b3e151..64ff380 100644
--- a/src/arm/Gex_tables.c
+++ b/src/arm/Gex_tables.c
@@ -53,12 +53,6 @@
     unw_dyn_info_t di;         /* info about the ARM exidx segment */
   };
 
-static inline uint32_t CONST_ATTR
-prel31_read (uint32_t prel31)
-{
-  return ((int32_t)prel31 << 1) >> 1;
-}
-
 static inline int
 prel31_to_addr (unw_addr_space_t as, void *arg, unw_word_t prel31,
 		unw_word_t *val)