powerpc/configs/6xx: Drop no longer selectable CONFIG_BT_HCIUART_LL

Since commit 76c4969f ("Bluetooth: hci_uart: fix kconfig
dependency") we can no longer select CONFIG_BT_HCIUART_LL.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/configs/ppc6xx_defconfig

@@ -331,7 +331,6 @@ CONFIG_BT_BNEP_PROTO_FILTER=y
 CONFIG_BT_HIDP=m
 CONFIG_BT_HCIUART=m
 CONFIG_BT_HCIUART_BCSP=y
-CONFIG_BT_HCIUART_LL=y
 CONFIG_BT_HCIBCM203X=m
 CONFIG_BT_HCIBPA10X=m
 CONFIG_BT_HCIBFUSB=m