input: sparse-keymap: use devm_kmemdup_array()

Convert to use devm_kmemdup_array() and while at it, use source size
instead of destination.

Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>