omap: add basic SPL support

- Provide alternate implementations of board_init_f()
  board_init_r() for OMAP spl.
- Provide linker script
- Initialize global data
- Add serial console support
- Update CONFIG_SYS_TEXT_BASE to allow for SPL's bss and move
  it to board config header from config.mk

Signed-off-by: Aneesh V <aneesh@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>
diff --git a/board/ti/sdp4430/Makefile b/board/ti/sdp4430/Makefile
index f1ee544..12f2743 100644
--- a/board/ti/sdp4430/Makefile
+++ b/board/ti/sdp4430/Makefile
@@ -25,7 +25,9 @@
 
 LIB	= $(obj)lib$(BOARD).o
 
+ifndef CONFIG_SPL_BUILD
 COBJS	:= sdp.o cmd_bat.o
+endif
 
 SRCS	:= $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS))