powerpc: Migrate HIGH_BATS to Kconfig

Migrate the CONFIG_HIGH_BATS variable to Kconfig.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/configs/sbc8641d_defconfig b/configs/sbc8641d_defconfig
index d1ffea5..47cec18 100644
--- a/configs/sbc8641d_defconfig
+++ b/configs/sbc8641d_defconfig
@@ -1,6 +1,7 @@
 CONFIG_PPC=y
 CONFIG_SYS_TEXT_BASE=0xfff00000
 CONFIG_MPC86xx=y
+CONFIG_HIGH_BATS=y
 CONFIG_TARGET_SBC8641D=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y