rmodule: add subsections to linker script

Depending on the compiler options, subsections of the form
of .section.subsection could be generated. Therefore, include
those subsections for .bss, .sbss, and .data.

Change-Id: I80dd64d8c62e7bc449ee2bbc0a22a941777e2ea6
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/5407
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>