pcmcia: Drop a bunch of unused CONFIG_SYS_PCMCIA_ macros

Last users of the following macros (for n = 0..7) were removed in
commit 5b8e76c3 ("powerpc, 8xx: remove support for 8xx"):

CONFIG_SYS_PCMCIA_PBRn
CONFIG_SYS_PCMCIA_PORn

Signed-off-by: Tuomas Tynkkynen <tuomas@tuxera.com>