MIPS: BCM47XX: fix kconfig dependency bug for BCM47XX_BCMA

When BCM47XX_BCMA is enabled and BCMA_DRIVER_PCI is disabled, it results
in the following Kbuild warning:

WARNING: unmet direct dependencies detected for BCMA_DRIVER_PCI_HOSTMODE
  Depends on [n]: MIPS [=y] && BCMA_DRIVER_PCI [=n] && PCI_DRIVERS_LEGACY [=y] && BCMA [=y]=y
  Selected by [y]:
  - BCM47XX_BCMA [=y] && BCM47XX [=y] && PCI [=y]

The reason is that BCM47XX_BCMA selects BCMA_DRIVER_PCI_HOSTMODE without
depending on or selecting BCMA_DRIVER_PCI while BCMA_DRIVER_PCI_HOSTMODE
depends on BCMA_DRIVER_PCI. This can also fail building the kernel.

Honor the kconfig dependency to remove unmet direct dependency warnings
and avoid any potential build failures.

Fixes: c1d1c5d4 ("bcm47xx: add support for bcma bus")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=209879


Signed-off-by: Necip Fazil Yildiran <fazilyildiran@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>