acpi: Disable ACPI table override if securelevel is set

From the kernel documentation (initrd_table_override.txt):

  If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible
  to override nearly any ACPI table provided by the BIOS with an
  instrumented, modified one.

When securelevel is set, the kernel should disallow any unauthenticated
changes to kernel space. ACPI tables contain code invoked by the kernel, so
do not allow ACPI tables to be overridden if securelevel is set.

Signed-off-by: Linn Crosetto <linn@hpe.com>
static void __init e820_add_kernel_range(void)
{
	u64 start = __pa_symbol(_text);
	u64 size = __pa_symbol(_end) - start;

	/*
	 * Complain if .text .data and .bss are not marked as E820_RAM and
	 * attempt to fix it by adding the range. We may have a confused BIOS,
	 * or the user may have used memmap=exactmap or memmap=xxM$yyM to
	 * exclude kernel range. If we really are running on top non-RAM,
	 * we will crash later anyways.
	 */
	if (e820_all_mapped(start, start + size, E820_RAM))
		return;

	pr_warn(".text .data .bss are not marked as E820_RAM!\n");
	e820_remove_range(start, size, E820_RAM, 0);
	e820_add_region(start, size, E820_RAM);
}

static void __init e820_add_kernel_range(void)
{
	u64 start = __pa_symbol(_text);
	u64 size = __pa_symbol(_end) - start;

	/*
	 * Complain if .text .data and .bss are not marked as E820_RAM and
	 * attempt to fix it by adding the range. We may have a confused BIOS,
	 * or the user may have used memmap=exactmap or memmap=xxM$yyM to
	 * exclude kernel range. If we really are running on top non-RAM,
	 * we will crash later anyways.
	 */
	if (e820_all_mapped(start, start + size, E820_RAM))
		return;

	pr_warn(".text .data .bss are not marked as E820_RAM!\n");
	e820_remove_range(start, size, E820_RAM, 0);
	e820_add_region(start, size, E820_RAM);
}
