efi/efivars: Set generic ops before loading SSDT

Efivars allows for overriding of SSDT tables, however starting with
commit

  bf67fad ("efi: Use more granular check for availability for variable services")

this use case is broken. When loading SSDT generic ops should be set
first, however mentioned commit reversed order of operations. Fix this
by restoring original order of operations.

Fixes: bf67fad ("efi: Use more granular check for availability for variable services")
Signed-off-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Link: https://lore.kernel.org/r/20201123172817.124146-1-amadeuszx.slawinski@linux.intel.com
Tested-by: Cezary Rojewski <cezary.rojewski@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/efi.c

@@ -390,10 +390,10 @@ static int __init efisubsys_init(void)
 
 	if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE |
 				      EFI_RT_SUPPORTED_GET_NEXT_VARIABLE_NAME)) {
-		efivar_ssdt_load();
 		error = generic_ops_register();
 		if (error)
 			goto err_put;
+		efivar_ssdt_load();
 		platform_device_register_simple("efivars", 0, NULL, 0);
 	}