davinci: DM644x: rename board file

Rename DM6446 EVM board file, no functional changes.  Code is updated
and reworked in following patch.

Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>

diff --git a/arch/arm/mach-davinci/board-evm.c b/arch/arm/mach-davinci/board-dm644x-evm.c
similarity index 100%
rename from arch/arm/mach-davinci/board-evm.c
rename to arch/arm/mach-davinci/board-dm644x-evm.c