boards/shields: waveshare_epaper: Move to conditional Kconfig

Move wavehare epaper shields to conditional Kconfig.
As part of this change, direct drivers Kconfig symbols enabling
(SPI, SSD16XX) are removed as they are application
responsibility. GPIO is removed as well as it should be 'y' by
default on  all boards according to Default board configuration
guidelines.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>