of: unittest: fix EXPECT text for gpio hog errors

of: unittest: fix EXPECT text for gpio hog errors

BugLink: https://bugs.launchpad.net/bugs/1951822
[ Upstream commit e85860e5bc077865a04f0a88d0b0335d3200484a ]

The console message text for gpio hog errors does not match
what unittest expects.

Fixes: f4056e705b2ef ("of: unittest: add overlay gpio test to catch gpio hog problem")
Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Link: https://lore.kernel.org/r/20211029013225.2048695-1-frowand.list@gmail.com
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>