rcar/module: add boost mode support

The following frequencies can be set with PERFORMANCE_LEVEL_SET:
 -1600000000 : 1600 MHz
 -1700000000 : 1700 MHz

Signed-off-by: Tsutomu Muroya <tsutomu.muroya.jy@bp.renesas.com>
Signed-off-by: Nicolas Royer <nroyer@baylibre.com>