parisc: Raise minimal GCC version to 12.0.0

Raise the minimum gcc version for parisc64 to 12.0.0 (for __int128 type)
and keep 5.1.0 as minimum for 32-bit parisc target.

Fixes: 8664645a ("parisc: Raise minimal GCC version")
Signed-off-by: Helge Deller <deller@gmx.de>