.gitignore: ignore Module.symvers in all directories

When using `make M=/path/to/driver modules` to build a module, file
Module.symvers will be created in that directory, so it's better to
ignore it in all directories.

Slightly reordered, let specific file names behind general ones.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kyungsik Lee <kyungsik.lee@lge.com>
Cc: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Zhao, Gang <gamerh2o@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>