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/xpedite517x_defconfig b/configs/xpedite517x_defconfig
index d2d8313..cad95d3 100644
--- a/configs/xpedite517x_defconfig
+++ b/configs/xpedite517x_defconfig
@@ -1,6 +1,7 @@
 CONFIG_PPC=y
 CONFIG_SYS_TEXT_BASE=0xfff00000
 CONFIG_MPC86xx=y
+CONFIG_HIGH_BATS=y
 CONFIG_TARGET_XPEDITE517X=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y