microblaze/PCI: Remove unused sys_pciconfig_iobase() and et al declaration

Removed unused code which provides information of various
I/O regions.

Signed-off-by: Thippeswamy Havalige <thippeswamy.havalige@amd.com>
Link: https://lore.kernel.org/r/20221025065214.4663-11-thippeswamy.havalige@amd.com


Signed-off-by: Michal Simek <michal.simek@amd.com>