powerpc: mpc512x: drop bogus and unused psc register bit definitions

These were introduced in commit 25ae3a07 ("[POWERPC] mpc512x: Add
MPC512x PSC support to MPC52xx psc driver") and never used. Moreover
according to the datasheet[1] MEMERROR is bit 25 (0x40) and ORERR is
bit 27 (0x10).

[1] MPC5125RM Rev. 2; 11/2009

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Anatolij Gustschin <agust@denx.de>