ARM: spitz: fix touchscreen max presure

This fixes max_pressure for spitz's touchscreen, and is requirement
for getting reasonable pressure numbers from touchscreen driver.

Signed-off-by: Pavel Machek <pavel@ucw.cz>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Eric Miao <eric.y.miao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>