[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/envsetup.sh b/envsetup.sh
index 6188f26..5c66a9e 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -136,9 +136,7 @@
         arm64) toolchaindir=aarch64/aarch64-linux-android-$targetgccversion/bin;
                toolchaindir2=arm/arm-linux-androideabi-$targetgccversion2/bin
             ;;
-        mips) toolchaindir=mips/mipsel-linux-android-$targetgccversion/bin
-            ;;
-        mips64) toolchaindir=mips/mips64el-linux-android-$targetgccversion/bin
+        mips|mips64) toolchaindir=mips/mips64el-linux-android-$targetgccversion/bin
             ;;
         *)
             echo "Can't find toolchain for unknown architecture: $ARCH"
@@ -980,8 +978,7 @@
    case "$ARCH" in
        arm) GDB=arm-linux-androideabi-gdb;;
        arm64) GDB=arm-linux-androideabi-gdb; GDB64=aarch64-linux-android-gdb;;
-       mips) GDB=mipsel-linux-android-gdb;;
-       mips64) GDB=mipsel-linux-android-gdb;;
+       mips|mips64) GDB=mips64el-linux-android-gdb;;
        x86) GDB=x86_64-linux-android-gdb;;
        x86_64) GDB=x86_64-linux-android-gdb;;
        *) echo "Unknown arch $ARCH"; return 1;;