[MIPS] Add optimized string functions

Use same string functions for all MIPS architectures.

Bug: 21555893
(cherry picked from commit 38f2eaa07b0ad2e01a40607d3a0ac240ff53abbf)

Change-Id: I94521f023d0bb136a4672782148a9f6e77cc6f1e
diff --git a/libc/arch-mips/mips.mk b/libc/arch-mips/mips.mk
index 33eceab..05e7198 100644
--- a/libc/arch-mips/mips.mk
+++ b/libc/arch-mips/mips.mk
@@ -6,6 +6,9 @@
 
 libc_bionic_src_files_mips += \
     arch-mips/string/memcmp.c \
+    arch-mips/string/memcpy.S \
+    arch-mips/string/memset.S \
+    arch-mips/string/strcmp.S \
     bionic/__memcpy_chk.cpp \
     bionic/__memset_chk.cpp \
     bionic/__strcpy_chk.cpp \
@@ -31,7 +34,6 @@
     upstream-openbsd/lib/libc/string/stpcpy.c \
     upstream-openbsd/lib/libc/string/stpncpy.c \
     upstream-openbsd/lib/libc/string/strcat.c \
-    upstream-openbsd/lib/libc/string/strcmp.c \
     upstream-openbsd/lib/libc/string/strcpy.c \
     upstream-openbsd/lib/libc/string/strlcat.c \
     upstream-openbsd/lib/libc/string/strlcpy.c \
@@ -54,14 +56,10 @@
 
 ifndef ARCH_MIPS_REV6
 libc_bionic_src_files_mips += \
-    arch-mips/string/memcpy.S \
-    arch-mips/string/memset.S \
     arch-mips/string/mips_strlen.c \
 
 else
 libc_bionic_src_files_mips += \
-    arch-mips/string/memcpy.c \
-    arch-mips/string/memset.c \
     arch-mips/string/strlen.c \
 
 endif