Blackfin arch: Add missing definitions of BF54x

#define                   PLL_OFF  0x2        /* Disable PLL */

#define                        DF  0x1        /* Divide Frequency */

/* SWRST Masks */

#define              SYSTEM_RESET 0x0007       /* Initiates A System Software Reset */

#define              DOUBLE_FAULT 0x0008       /* Core Double Fault Causes Reset */

#define              RESET_DOUBLE 0x2000       /* SW Reset Generated By Core Double-Fault */

#define                RESET_WDOG 0x4000       /* SW Reset Generated By Watchdog Timer */

#define            RESET_SOFTWARE 0x8000       /* SW Reset Occurred Since Last Read Of SWRST */

/* Bit masks for PLL_STAT */

#define                PLL_LOCKED  0x20       /* PLL Locked Status */