efi: Drop minimum EFI version check at boot

We currently pass a minimum major version to the generic EFI helper that
checks the system table magic and version, and refuse to boot if the
value is lower.

The motivation for this check is unknown, and even the code that uses
major version 2 as the minimum (ARM, arm64 and RISC-V) should make it
past this check without problems, and boot to a point where we have
access to a console or some other means to inform the user that the
firmware's major revision number made us unhappy. (Revision 2.0 of the
UEFI specification was released in January 2006, whereas ARM, arm64 and
RISC-V support where added in 2009, 2013 and 2017, respectively, so
checking for major version 2 or higher is completely arbitrary)

So just drop the check.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>