MIPS: BCM47xx: Don't select BCMA_HOST_PCI

MIPS: BCM47xx: Don't select BCMA_HOST_PCI

SoC may have non-Broadcom PCI device attached or one may want to use
totally different PCI driver.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: https://patchwork.linux-mips.org/patch/10537/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>