config/arm: fix variable names

config/arm: fix variable names

A config variable rename seems missed to update all config files and new
config file get with old variable names.

Reflect config variable rename to all config files, changed
'implementor_id' to 'implementer_id',
'implementor_pn' to 'part_number'.

Fixes: 3d01d65ba0d3 ("config: add aarch64 clang for Ubuntu 18.04")
Fixes: 7870ae8994c6 ("config/arm: rename variables")

Reported-by: Thierry Herbelot <thierry.herbelot@6wind.com>
Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Juraj Linkeš <juraj.linkes@pantheon.tech>