linux-wandboard

Input: tsc2007 - make init/exit platform hw callbacks optional

Make init_platform_hw and exit_platform_hw callbacks optional since
they are not needed on all platforms.

Signed-off-by: Richard Röjfors <richard.rojfors.ext@mocean-labs.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>