checkpatch: fix $Float creation of match variables

Commit 74349bcc ("checkpatch: add support for floating point
constants") added an unnecessary match variable that caused tests that
used a $Constant or $LvalOrFunc to have one too many matches.

This causes problems with usleep_range, min/max and other extended
tests.

Avoid using match variables in $Float.
Avoid using match variables in $Assignment too.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>