doc: slight cleanup of MASM compatibility package information
doc: slight cleanup of MASM compatibility package information

Note that the extended DB syntax is also available, regardless of if
%use masm is used or not.

Signed-off-by: H. Peter Anvin (Intel) <8a453bad9912ffe59bc0f0b8abe03df9be19379e@zytor.com>

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