davinci: macro rename DA8XX_LPSC0_DMAX to DA8XX_LPSC0_PRUSS.

DMAX is an internal name for the module which is
known as PRUSS in TI public documentation. This patch just
gets the code in sync with TI documentation.

Signed-off-by: Subhasish Ghosh <subhasish@mistralsolutions.com>
Acked-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>