ARM: DRA7: hwmod: Fix boot crash with DEBUG_LL enabled on UART3

With commit '7dedd346: ARM: OMAP2+: hwmod: Fix a crash in _setup_reset()
with DEBUG_LL' we moved from parsing cmdline to identify uart used
for earlycon to using the requsite hwmod CONFIG_DEBUG_OMAPxUARTy FLAGS.

On DRA7 UART3 hwmod doesn't have this flag enabled, and atleast on
BeagleBoard-X15, where we use UART3 for console, boot fails with
DEBUG_LL enabled. Enable DEBUG_OMAP4UART3_FLAGS for UART3 hwmod.

For using DEBUG_LL, enable CONFIG_DEBUG_OMAP4UART3 in menuconfig.

Fixes: 90020c7b ("ARM: OMAP: DRA7: hwmod: Create initial DRA7XX SoC data")
Cc: <stable@vger.kernel.org> # v3.12+
Reviewed-by: Felipe Balbi <balbi@ti.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>