Revert MMIO space writes on shutdown as needed

Reversible MMIO space writes now use rmmio_write*().
Reversible PCI MMIO space writes now use pci_rmmio_write*().
If a MMIO value needs to be queued for restore without writing it,
use rmmio_val*().
MMIO space writes which are one-shot (e.g. communication with some chip)
should continue to use the permanent mmio_write* variants.

Corresponding to flashrom svn r1292.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>

David tested it successfully on some NM10/ICH7 platforms which switch
between SPI and LPC targets (x86 BIOS ROM vs. EC firmware ROM).

Acked-by: David Hendricks <dhendrix@google.com>
diff --git a/nicintel_spi.c b/nicintel_spi.c
index 3882e81..28d332e 100644
--- a/nicintel_spi.c
+++ b/nicintel_spi.c
@@ -148,6 +148,11 @@
 
 	nicintel_spibar = physmap("Intel Gigabit NIC w/ SPI flash",
 				  io_base_addr, 4096);
+	/* Automatic restore of EECD on shutdown is not possible because EECD
+	 * does not only contain FLASH_WRITES_DISABLED|FLASH_WRITES_ENABLED,
+	 * but other bits with side effects as well. Those other bits must be
+	 * left untouched.
+	 */
 	tmp = pci_mmio_readl(nicintel_spibar + EECD);
 	tmp &= ~FLASH_WRITES_DISABLED;
 	tmp |= FLASH_WRITES_ENABLED;
@@ -167,6 +172,9 @@
 {
 	uint32_t tmp;
 
+	/* Disable writes manually. See the comment about EECD in
+	 * nicintel_spi_init() for details.
+	 */
 	tmp = pci_mmio_readl(nicintel_spibar + EECD);
 	tmp &= ~FLASH_WRITES_ENABLED;
 	tmp |= FLASH_WRITES_DISABLED;