powerpc, 8xx: move Serial driver to drivers/serial/

At the same time, move to Kconfig

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index dca31b2..72a6996 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -48,6 +48,7 @@
 obj-$(CONFIG_BCM283X_MU_SERIAL) += serial_bcm283x_mu.o
 obj-$(CONFIG_MSM_SERIAL) += serial_msm.o
 obj-$(CONFIG_MVEBU_A3700_UART) += serial_mvebu_a3700.o
+obj-$(CONFIG_MPC8XX_CONS) += serial_mpc8xx.o
 
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_USB_TTY) += usbtty.o