Restore pcm051_rev3_defconfig config

pcm051_rev3_defconfig config (Phytec Wega board) has been dropped in

    64efd11d ("arm: Remove pcm051 board")

due to expired migration deadlines. Here, pcm051_rev3_defconfig support is
reintroduced.

Signed-off-by: Matwey V. Kornilov <matwey.kornilov@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>