PCI: brcmstb: Use same constant table for config space access

PCI: brcmstb: Use same constant table for config space access

The constants EXT_CFG_DATA and EXT_CFG_INDEX vary by SoC, where one of
the map_bus methods used these constants, and the other used a different
set of constants.

Thankfully, there was no problem because the SoCs that used the latter
map_bus method all had the same register constants.

Thus, remove redundant constants and adjust the code to use the correct
constants accordingly.

While at it, update the value of EXT_CFG_DATA to use the 4k-page based
configuration space access system, which is what the second map_bus
method was already using.

Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20250214173944.47506-7-james.quinlan@broadcom.com
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>