The module load address always needs to be included when setting the dm_*_va
fields of dt_module_t. Previously, this was only done on architectures where
kernel modules have type ET_REL; this change fixes that. As a result, symbol
name resolution in the stack() action now works properly for kernel modules
on i386.

Reported by:	Shrikanth Kamath <shrikanth07@gmail.com>
Tested by:	Shrikanth Kamath
Discussed with:	avg
MFC after:	2 weeks
Adjust some checks missed in r274637, now that pi_rname can be NULL.

Additionally fix a misparenthesization in the same check, noticed while
fixing the first bug. This bug only appears to cause problems if the same
USDT probe appears twice within a static function.

X-MFC-With:	r274637