ALSA: HDA: Fix internal mic on Dell E5420/E5520

This is a fixup for the 2.6.38 kernel, as the issue is being resolved
by upstream commits 699d8995 and
094a4245 - which are too invasive
to reach 2.6.38. Instead make pin fixes as a workaround.

BugLink: http://bugs.launchpad.net/bugs/740055


Tested-by: Kent Baxley <kent.baxley@canonical.com>
Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Acked-by: Takashi Iwai <tiwai@suse.de>