x86/MCE/AMD: Define a function to get SMCA bank type

Scalable MCA systems have various types of banks. The bank's type
can determine how we handle errors from it. For example, if a bank
represents a UMC (Unified Memory Controller) then we will need to
convert its address from a normalized address to a system physical
address before handling the error.

[ bp: Verify m->bank is within range and use bank pointer. ]

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20171207203955.118171-1-Yazen.Ghannam@amd.com