blackfin: convert blackfin board_f and board_r to use generic board init functions

- move blackfin specific cpu init code from blackfin board.c to cpu.c
- remove blackfin specific board init code and invoke generic board_f fron cpu init entry
- rename section name bss_vma to bss_start in order to match the generic board init code
- add a fake relocate_code function to set up the new stack only

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>

include/configs/bf533-stamp.h

@@ -98,10 +98,11 @@
  */
 #define CONFIG_BFIN_SPI
 #define CONFIG_ENV_SPI_MAX_HZ	30000000
+/*
 #define CONFIG_SF_DEFAULT_SPEED	30000000
 #define CONFIG_SPI_FLASH
 #define CONFIG_SPI_FLASH_ALL
-
+*/
 
 /*
  * Env Storage Settings