assemble.c: for the signed byte operand, check overflow then rawbyte
assemble.c: for the signed byte operand, check overflow then rawbyte

When we are generating a signed byte operand, we anyway have to do the
overflow check "manually".  After doing so, output the result using
out_rawbyte() instead of out_imm(), so we don't end up doing a
redundant, and incorrect, second overflow check.

Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@linux.intel.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm