BeagleBoardPkg: remove unused modules

BeagleBoardPkg: remove unused modules

Commit 0bade1054db7 ("BeagleBoardPkg: Replaced the original DSC/FDF files
by their new versions that use the ARM Platform Framework"), which dates
back to 2011, modified BeagleBoardPkg to replace references to its Sec.inf,
Bds.inf and some of its library implementations to refer to versions under
ArmPlatformPkg instead. Since the original modules have been unused ever
since, we can safely remove them now.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>