arch/arm: some cores have a different name with gcc-9

arch/arm: some cores have a different name with gcc-9

In gcc-9, some cores from the ThunderX familly have been renamed to
their marketting names, i.e. OcteonTX. Subsequently, new core names
have been added to gcc, with the old names still being around.

Update the prompts with the new names as alternative to the existing
names. We still keep the kconfig options as-is, so that we do not need
to add legacy handling.

However, since there is no guarantee for how long gcc will retain
compatibility for the older names, we readily switch over to using the
new names when using a gcc 9-or-later, but keep using the older names
with gcc older than 9.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
[Arnout: don't rely on ordering, but make condition explicit]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>