src/arch/x86/acpi.c: Use correct host address width in DMAR ACPI table

The previous implementation assumed the CPU physical address size to
be 40 which is not true of all platforms. Use an existing function to
obtain the correct CPU physical address to report in the DMAR ACPI
table.

Change-Id: Ia79e9dadecc3f5f6a86ce3789b213222bef482b3
Signed-off-by: Jacob Laska <jlaska91@gmail.com>
Reviewed-on: https://review.coreboot.org/14102
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/arch/x86/acpi.c

@@ -411,7 +411,7 @@ void acpi_create_dmar(acpi_dmar_t *dmar, enum dmar_flags flags,
 	header->length = sizeof(acpi_dmar_t);
 	header->revision = 1;
 
-	dmar->host_address_width = 40 - 1; /* FIXME: == MTRR size? */
+	dmar->host_address_width = cpu_phys_address_size() - 1;
 	dmar->flags = flags;
 
 	current = acpi_fill_dmar(current);