soc/amd/stoneyridge: Add ACPI MMIO enable function

In preparation for moving AGESA calls out of bootblock:
* Add definitions for needed registers in southbridge.h
* Add function to enable AMD FCH ACPI MMIO regions 0xfed80000 to
  0xfed81ffff.  Will be called by a later commit.

BUG=b:65442212
BRANCH=master
TEST=abuild, build Gardenia, build boot Grunt (with other changes
to call code not committed at this time)

Change-Id: If26efa6c6f5b562ba898e7d9da4827833310dc26
Signed-off-by: Garrett Kirkendall <garrett.kirkendall@amd.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/25025
Reviewed-by: Richard Spiegel <richard.spiegel@silverbackltd.com>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/stoneyridge/southbridge.c

@@ -367,6 +367,18 @@ void sb_lpc_decode(void)
 	pci_write_config32(SOC_LPC_DEV, LPC_IO_PORT_DECODE_ENABLE, tmp);
 }
 
+void sb_acpi_mmio_decode(void)
+{
+	uint8_t byte;
+
+	/* Enable ACPI MMIO range 0xfed80000 - 0xfed81fff */
+	outb(PM_ISA_CONTROL, PM_INDEX);
+	byte = inb(PM_DATA);
+	byte |= MMIO_EN;
+	outb(PM_ISA_CONTROL, PM_INDEX);
+	outb(byte, PM_DATA);
+}
+
 void sb_clk_output_48Mhz(void)
 {
 	u32 ctrl;