Input: matrix_keypad - replace header inclusions by forward declarations

When the data structure is only referred by pointer, compiler may not need
to see the contents of the data type. Thus, we may replace header inclusions
by respective forward declarations.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220923184632.2157-2-andriy.shevchenko@linux.intel.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>