arch: rename the SUPPORT_XXX options

First, 'SUPPORT' should be spelled 'SUPPORTS'.

Second, 'SUPPORT_XXX' really means 'supports --with-xxx', so rename the
affected options accordingly. Update the affected archs to match the new
namings.

Reported-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 # Compute Alpha-specific values

 CT_DoArchTupleValues () {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}${CT_ARCH_ALPHA_VARIANT}"

 }