x86/boot: Clear RSDP address in boot_params for broken loaders

Gunnar Krueger reported a systemd-boot failure and bisected it down to:

  e6e094e ("x86/acpi, x86/boot: Take RSDP address from boot params if available")

In case a broken boot loader doesn't clear its 'struct boot_params', clear
rsdp_addr in sanitize_boot_params().

Reported-by: Gunnar Krueger <[email protected]>
Tested-by: Gunnar Krueger <[email protected]>
Signed-off-by: Juergen Gross <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Fixes: e6e094e ("x86/acpi, x86/boot: Take RSDP address from boot params if available")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

arch/x86/include/asm/bootparam_utils.h

@@ -36,6 +36,7 @@ static void sanitize_boot_params(struct boot_params *boot_params)
 	 */
 	if (boot_params->sentinel) {
 		/* fields in boot_params are left uninitialized, clear them */
+		boot_params->acpi_rsdp_addr = 0;
 		memset(&boot_params->ext_ramdisk_image, 0,
 		       (char *)&boot_params->efi_info -
 			(char *)&boot_params->ext_ramdisk_image);