efi: adjust ebbr to v2.1 in conformance profile

The EFI Conformance Profile Table entry for EBBR appears in v2.1.0 of the
EBBR specification[1]. Update naming accordingly.

While at it, update the EBBR version referenced in the documentation.

[1]: https://github.com/ARM-software/ebbr/releases/tag/v2.1.0



Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>