[MIPS] Unite mipsel and mips64el 4.9 gcc toolchains

Use 4.9 mips64el toolchain for both 64- and 32-bit builds.
Tell ld when 32-bit links are required.
Override 4.9's changed defaults for mips floating point
register use, to get same assembler rules as 4.8 and earlier.

Also: drop unused  soft-fp build targets, cleanout redundant
compiler options, and remove extraneous Android.mk file.

Change-Id: I86f1075266349edb2b08a7709b9f5472d8cfda32
diff --git a/core/clang/TARGET_mips.mk b/core/clang/TARGET_mips.mk
index de615b0..0107519 100644
--- a/core/clang/TARGET_mips.mk
+++ b/core/clang/TARGET_mips.mk
@@ -3,7 +3,7 @@
 
 CLANG_CONFIG_mips_TARGET_TRIPLE := mipsel-linux-android
 CLANG_CONFIG_mips_TARGET_TOOLCHAIN_PREFIX := \
-  $($(clang_2nd_arch_prefix)TARGET_TOOLCHAIN_ROOT)/$(CLANG_CONFIG_mips_TARGET_TRIPLE)/bin
+  $($(clang_2nd_arch_prefix)TARGET_TOOLCHAIN_ROOT)/mips64el-linux-android/bin
 
 CLANG_CONFIG_mips_TARGET_EXTRA_ASFLAGS := \
   $(CLANG_CONFIG_EXTRA_ASFLAGS) \