ArmPlatformPkg: break out juno revision detection
ArmPlatformPkg: break out juno revision detection

The code to detect what juno revision we are running on
is fairly small put it in a common header where it may be
used in a couple places.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeremy Linton <5fd20647ba5fc84c5334ca74068125bbbd19ac4e@arm.com>
Reviewed-by: Leif Lindholm <a613079f0455438b29e28a9c5b9eb3779a81a33a@linaro.org>

MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2