assemble.c: always do overflow warnings on pass 2
assemble.c: always do overflow warnings on pass 2

It is very rare that it makes sense to warn on pass 1.  Instead, do
all the overflow warnings in pass 2.

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

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