kmtegr1: Drop CONFIG_KMTEGR1

The only usage of CONFIG_KMTEGR1 can be replaced by
CONFIG_TARGET_KMTEGR1 so do so and remove this other symbol.

Cc: Holger Brunck <holger.brunck@hitachienergy.com>
Cc: Heiko Schocher <hs@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Holger Brunck <holger.brunck@hitachienergy.com>