dm6467Tevm: Use a common configuration file for davinci_dm6467evm and davinci_dm6467Tevm

In commit 2d575e46 a separate header
file was introduced for the DM6467T EVM, include/configs/davinci_dm6467Tevm.h.
The substantial difference between the davinci_dm6467evm and the
davinci_dm6467Tevm configuration is a single bit in the hardware revision
that is passed to the Linux kernel and davinci_dm6467evm has
REFCLK_FREQ = 27000000 where as davinci_dm6467Tevm.h has a
REFCLK_FREQ = 33000000.

This patch removes include/configs/davinci_dm6467Tevm.h. Instead the
include/configs/davinci_dm6467evm.h configuration is used for DM6467T EVMs and
renamed CFG_REFCLK_FREQ to CONFIG_REFCLK_FREQ and CONFIG_REFCLK_FREQ is defined
in boards.cfg.

Signed-off-by: Prabhakar Lad <prabhakar.csengg@gmail.com>
Cc: Tom Rini <trini@ti.com>