MFD_CORE depends on HAS_IOMEM so anything that selects MFD_CORE should
also depend on HAS_IOMEM since 'select' does not check any dependencies
of the symbol that is being selected.

Prevents this kconfig warning:

WARNING: unmet direct dependencies detected for MFD_CORE
  Depends on [n]: HAS_IOMEM [=n]
  Selected by [m]:
  - HI6421V600_IRQ [=m] && OF [=y] && SPMI [=m]

Fixes: bb3b6552 ("staging: hikey9xx: split hi6421v600 irq into a separate driver")
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20211004001641.23180-1-rdunlap@infradead.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>