kbuild: fix false section mismatch warnings

Darren Jenkins <darrenrjenkins@gmail.com> pointed out a
number of false positives where we referenced variables
from a _driver variable.
Fix it by check for that pattern and ignore it.

Randy.Dunlap <rdunlap@xenotime.net> pointed out a similar
set of warnings for a number of scsi drivers.
In scsi world they misname their variables *_template or
*_sht so add these to list of variables that may have references
to .init.text with no warning.

Randy.Dunlap <rdunlap@xenotime.net> also pointed out a scsi driver
with many references to .exit.text from .rodata. This is compiler
generated references and we already ignore these for .init.text, so
ignore them for .exit.text also.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>