ast: Account for differences between 2400 vs 2500
ast: Account for differences between 2400 vs 2500

Currently astbmc_early_init() only applies to AST2400/POWER8.

This fixes the code so it also applies to AST2500/POWER9 except for
the PSI BAR fixup which is not needed on AST2500/POWER9.

Signed-off-by: Michael Neuling <7b0ab45a730e48a69239010b5b8fe5fa4e8eaac6@neuling.org>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

qemu/skiboot,mikey/skiboot,stewart-ibm/skiboot,shenki/skiboot,legoater/skiboot,shenki/skiboot,legoater/skiboot,stewart-ibm/skiboot,legoater/skiboot,qemu/skiboot,open-power/skiboot,open-power/skiboot,open-power/skiboot,legoater/skiboot,shenki/skiboot,mikey/skiboot,qemu/skiboot,legoater/skiboot,qemu/skiboot,open-power/skiboot,shenki/skiboot,stewart-ibm/skiboot,mikey/skiboot,open-power/skiboot,shenki/skiboot,qemu/skiboot