arch-mips.inc: Add the MIPS ABIEXTENSION to toolchain name

arch-mips.inc: Add the MIPS ABIEXTENSION to toolchain name

[YOCTO #7143]

When the system is configured for a multilib SDK, such as:

require conf/multilib.conf
MULTILIBS = "multilib:lib32 multilib:lib64"
DEFAULTTUNE = "mips32r2"
DEFAULTTUNE_virtclass-multilib-lib32 = "mips64-n32"
DEFAULTTUNE_virtclass-multilib-lib64 = "mips64"

Only one of the mips64-n32 or mips64 toolchains is built.  Causing the
other to be unavailable.  This is due to both recipes ending up with the
same PN.

The toolchain uses the TRANSLATED_TARGET_ARCH in it's name, however the
target for mips64 and mips64 n32 were the same, causing the conflict.
Avoid this conflict by adding the ABIEXTENSION to the name.

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>