Input: tegra-kbc - remove default keymap

Tegra KBC driver have the default key mapping for 16x8 configuration.
The key mapping can be provided through platform data or through DT
and the mapping varies from platform to platform, hence this default
mapping is not so useful. Remove the default mapping to reduce the code
lines of the driver.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>