fbcon: Fix typo and bogus logic in get_default_font

Reported in: Bugzilla Bug 8727

Fix typo and bogus logic in get_default_font(). The bug results in
get_default_font() returning a font that may not be displayed properly by a
framebuffer driver.

Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>