mfd: dm355evm_msp: Convert LEDs to GPIO descriptor table

This converts the DaVinci DM355EVM LEDs to use GPIO descriptor look-ups.

Cc: Sekhar Nori <nsekhar@ti.com>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>