tcg: remove softfloat from --disable-tcg builds

Even though the presence of softfloat does not cause --disable-tcg builds to fail,
it is the single largest .o file in them.  Remove it, since TCG is the only client.
Acked-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Makefile.target

@@ -97,7 +97,7 @@ obj-$(CONFIG_TCG) += tcg/tcg.o tcg/tcg-op.o tcg/tcg-op-vec.o tcg/tcg-op-gvec.o
 obj-$(CONFIG_TCG) += tcg/tcg-common.o tcg/optimize.o
 obj-$(CONFIG_TCG_INTERPRETER) += tcg/tci.o
 obj-$(CONFIG_TCG_INTERPRETER) += disas/tci.o
-obj-y += fpu/softfloat.o
+obj-$(CONFIG_TCG) += fpu/softfloat.o
 obj-y += target/$(TARGET_BASE_ARCH)/
 obj-y += disas.o
 obj-$(call notempty,$(TARGET_XML_FILES)) += gdbstub-xml.o