staging: bcm2835-audio: delete TODO

Delete TODO since all tasks were completed:

1 - fixed here:
https://lore.kernel.org/all/20220408150359.26661-1-athierry@redhat.com/

2 - there are no remaining checkpatch.pl errors or warnings
Signed-off-by: Adrien Thierry <athierry@redhat.com>
Link: https://lore.kernel.org/r/20220420174401.305964-1-athierry@redhat.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/bcm2835-audio/TODO

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-*                           TODO: BCM2835-AUDIO                             *
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-1) Revisit multi-cards options and PCM route mixer control (as per comment
-https://lore.kernel.org/lkml/s5hd0to5598.wl-tiwai@suse.de)
-
-2) Fix the remaining checkpatch.pl errors and warnings.