target/i386: remove CC_OP_CLR

target/i386: remove CC_OP_CLR

Just use CC_OP_EFLAGS; it is not that likely that the flags computed by
CC_OP_CLR survive the end of the basic block, in which case there is no
need to spill cc_op_src.

cc_op_src now does need spilling if the XOR is followed by a memory
operation, but this only costs 0.2% extra TCG ops.  They will be recouped
by simplifications in how QEMU evaluates ZF at runtime, which are even
greater with this change.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>