[SCSI] aic79xx: fix MMIO for PPC 44x platforms

The driver stores the PCI resource address into 'u_long' variable before
calling ioremap_nocache() on it. This warrants kernel oops when the registers
are accessed on PPC 44x platforms which (being 32-bit) have PCI memory space
mapped beyond 4 GB.

The arch/ppc/ kernel has a fixup in ioremap() that helps create an illusion
that the PCI memory resources are mapped below 4 GB, but arch/powerpc/ code
got rid of this trick, having instead CONFIG_RESOURCES_64BIT enabled.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>