fix default size handling in monitor

fix default size handling in monitor

If /i format is used once (with x/xp/p command) default_fmt_size is set
to -1 and subsequent commands of the form /x outputs nothing. Included
patched fixes this by setting default_fmt_size only if the command is
not of format /i.

Signed-off-by: Gleb Natapov <gleb@qumranet.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5381 c046a42c-6fe2-441c-8c8c-71466251a162