Simple Text Input Ex Protocol tests can be skipped when the SCT is unable
to locate the console device bound to the protocol. This is the case with
U-Boot.

EBBR has requirements on the console, but it does not specifically require
that a device be always bound to the Simple Text Input Ex Protocol.

Simply ignore this skipped test instead of waiving it.

Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>