drivers/firmware: const-ify DMI API and internals

Three main sets of changes:

1) dmi_get_system_info() return value should have been marked const,
   since callers should not be changing that data.

2) const-ify DMI internals, since DMI firmware tables should,
   whenever possible, be marked const to ensure we never ever write to
   that data area.

3) const-ify DMI API, to enable marking tables const where possible
   in low-level drivers.

And if we're really lucky, this might enable some additional
optimizations on the part of the compiler.

The bulk of the changes are #2 and #3, which are interrelated.  #1 could
have been a separate patch, but it was so small compared to the others,
it was easier to roll it into this changeset.

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/arch/i386/kernel/acpi/boot.c b/arch/i386/kernel/acpi/boot.c
index cacdd88..afd2afe 100644
--- a/arch/i386/kernel/acpi/boot.c
+++ b/arch/i386/kernel/acpi/boot.c
@@ -907,7 +907,7 @@
 
 #ifdef __i386__
 
-static int __init disable_acpi_irq(struct dmi_system_id *d)
+static int __init disable_acpi_irq(const struct dmi_system_id *d)
 {
 	if (!acpi_force) {
 		printk(KERN_NOTICE "%s detected: force use of acpi=noirq\n",
@@ -917,7 +917,7 @@
 	return 0;
 }
 
-static int __init disable_acpi_pci(struct dmi_system_id *d)
+static int __init disable_acpi_pci(const struct dmi_system_id *d)
 {
 	if (!acpi_force) {
 		printk(KERN_NOTICE "%s detected: force use of pci=noacpi\n",
@@ -927,7 +927,7 @@
 	return 0;
 }
 
-static int __init dmi_disable_acpi(struct dmi_system_id *d)
+static int __init dmi_disable_acpi(const struct dmi_system_id *d)
 {
 	if (!acpi_force) {
 		printk(KERN_NOTICE "%s detected: acpi off\n", d->ident);
@@ -942,7 +942,7 @@
 /*
  * Limit ACPI to CPU enumeration for HT
  */
-static int __init force_acpi_ht(struct dmi_system_id *d)
+static int __init force_acpi_ht(const struct dmi_system_id *d)
 {
 	if (!acpi_force) {
 		printk(KERN_NOTICE "%s detected: force use of acpi=ht\n",