efi: efivars: limit availability to X86 builds

CONFIG_EFI_VARS controls the code that exposes EFI variables via
sysfs entries, which was deprecated before support for non-Intel
architectures was added to EFI. So let's limit its availability
to Intel architectures for the time being, and hopefully remove
it entirely in the not too distant future.

While at it, let's remove the module alias so that the module is
no longer loaded automatically.

Signed-off-by: Ard Biesheuvel <[e-mail]>

Documentation/arm/uefi.rst

···
 For actually enabling [U]EFI support, enable:
 
 - CONFIG_EFI=y
-- CONFIG_EFI_VARS=y or m
+- CONFIG_EFIVAR_FS=y or m
 
 The implementation depends on receiving information about the UEFI environment
 in a Flattened Device Tree (FDT) - so is only available with CONFIG_OF.

drivers/firmware/efi/Kconfig

···
 
 config EFI_VARS
 	tristate "EFI Variable Support via sysfs"
-	depends on EFI
+	depends on EFI && (X86 || IA64)
 	default n
 	help
 	  If you say Y here, you are able to get EFI (Extensible Firmware
 	  Interface) variable information via sysfs.  You may read,
 	  write, create, and destroy EFI variables through this interface.
-
-	  Note that using this driver in concert with efibootmgr requires
-	  at least test release version 0.5.0-test3 or later, which is
-	  available from:
-	  <http://linux.dell.com/efibootmgr/testing/efibootmgr-0.5.0-test3.tar.gz>
-
-	  Subsequent efibootmgr releases may be found at:
-	  <http://github.com/vathpela/efibootmgr>
+	  Note that this driver is only retained for compatibility with
+	  legacy users: new users should use the efivarfs filesystem
+	  instead.
 
 config EFI_ESRT
 	bool

drivers/firmware/efi/efivars.c

···
 MODULE_DESCRIPTION("sysfs interface to EFI Variables");
 MODULE_LICENSE("GPL");
 MODULE_VERSION(EFIVARS_VERSION);
-MODULE_ALIAS("platform:efivars");
 
 static LIST_HEAD(efivar_sysfs_list);