x86/acpi: Correct out-of-date comment of __acpi_map_table()

The implementation of function __acpi_map_table() has been
changed long time ago, and now it directly invokes
early_ioremap() to setup the temporarily acpi table mappings.

So correct its out-of-date comment.
Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: len.brown@intel.com
Cc: pavel@ucw.cz
Cc: rjw@sisk.pl
Link: http://lkml.kernel.org/r/51EE7F1C.9020506@gmail.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/acpi/boot.c

@@ -141,16 +141,8 @@ static u32 irq_to_gsi(int irq)
 }
 
 /*
- * Temporarily use the virtual area starting from FIX_IO_APIC_BASE_END,
- * to map the target physical address. The problem is that set_fixmap()
- * provides a single page, and it is possible that the page is not
- * sufficient.
- * By using this area, we can map up to MAX_IO_APICS pages temporarily,
- * i.e. until the next __va_range() call.
- *
- * Important Safety Note:  The fixed I/O APIC page numbers are *subtracted*
- * from the fixed base.  That's why we start at FIX_IO_APIC_BASE_END and
- * count idx down while incrementing the phys address.
+ * This is just a simple wrapper around early_ioremap(),
+ * with sanity checks for phys == 0 and size == 0.
  */
 char *__init __acpi_map_table(unsigned long phys, unsigned long size)
 {
@@ -160,6 +152,7 @@ char *__init __acpi_map_table(unsigned long phys, unsigned long size)
 
 	return early_ioremap(phys, size);
 }
+
 void __init __acpi_unmap_table(char *map, unsigned long size)
 {
 	if (!map || !size)