davinci: split out some dm644x-specific bits from psc

Split out DaVinci DM6446-specific bits from more generic bits:

 - Add a CONFIG_SOC_DM644X.  All current boards use DM6446 chips;
   DM6443 and DM6441 chips differ in available peripherals.

 - Move most DM644X-specific bits from psc.c to a new dm644x.c file,
   which is conditionally built.  It provides device-specific setup.

Plus minor coding style and comment updates with respect to the PSC.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

include/configs/davinci_dvevm.h

@@ -59,6 +59,7 @@
 #define CONFIG_SYS_TIMERBASE		0x01c21400	/* use timer 0 */
 #define CONFIG_SYS_HZ_CLOCK		27000000	/* Timer Input clock freq */
 #define CONFIG_SYS_HZ			1000
+#define CONFIG_SOC_DM644X
 /*====================================================*/
 /* EEPROM definitions for Atmel 24C256BN SEEPROM chip */
 /* on Sonata/DV_EVM board. No EEPROM on schmoogie.    */

include/configs/davinci_schmoogie.h

@@ -34,6 +34,7 @@
 #define CONFIG_SYS_TIMERBASE		0x01c21400	/* use timer 0 */
 #define CONFIG_SYS_HZ_CLOCK		27000000	/* Timer Input clock freq */
 #define CONFIG_SYS_HZ			1000
+#define CONFIG_SOC_DM644X
 /*=============*/
 /* Memory Info */
 /*=============*/

include/configs/davinci_sffsdr.h

@@ -35,6 +35,7 @@
 #define CONFIG_SYS_TIMERBASE		0x01c21400	/* use timer 0 */
 #define CONFIG_SYS_HZ_CLOCK		27000000	/* Timer Input clock freq */
 #define CONFIG_SYS_HZ			1000
+#define CONFIG_SOC_DM644X
 /* EEPROM definitions for Atmel 24LC64 EEPROM chip */
 #define CONFIG_SYS_I2C_EEPROM_ADDR_LEN		2
 #define CONFIG_SYS_I2C_EEPROM_ADDR		0x50

include/configs/davinci_sonata.h

@@ -59,6 +59,7 @@
 #define CONFIG_SYS_TIMERBASE		0x01c21400	/* use timer 0 */
 #define CONFIG_SYS_HZ_CLOCK		27000000	/* Timer Input clock freq */
 #define CONFIG_SYS_HZ			1000
+#define CONFIG_SOC_DM644X
 /*====================================================*/
 /* EEPROM definitions for Atmel 24C256BN SEEPROM chip */
 /* on Sonata/DV_EVM board. No EEPROM on schmoogie.    */