mpc83xx: Remove CONFIG_SYS_GPIO{1/2}_PRELIM and related

Last use of CONFIG_SYS_GPIO1_PRELIM was removed by
commit fae2ea59 ("ppc: Remove MPC8349EMDS board and ARCH_MPC8349
support").

Last use of CONFIG_SYS_GPIO2_PRELIM was removed even before by
commit 68438623 ("ppc: Remove caddy2 / vme8349 boards")

Those two items were removed from whitelist by
commit 8cca60a2 ("Kconfig: Remove some symbols from the whitelist")

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Fixes: fae2ea59 ("ppc: Remove MPC8349EMDS board and ARCH_MPC8349 support")