MIPS: kconfig: merge targets qemu_mips and qemu_mips64

Now the user can separately select the CPU type. Thus the
targets qemu_mips and qemu_mips64 can be merged to a single
target.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/configs/qemu_mips_defconfig b/configs/qemu_mips_defconfig
index 0a385af..f58dd22 100644
--- a/configs/qemu_mips_defconfig
+++ b/configs/qemu_mips_defconfig
@@ -1,3 +1,4 @@
 CONFIG_MIPS=y
 CONFIG_TARGET_QEMU_MIPS=y
 CONFIG_SYS_BIG_ENDIAN=y
+CONFIG_CPU_MIPS32_R2=y