blackfin: Fix using gd->baudrate before setting its value

Current code uses gd->baudrate before setting its value.
Besides, I got below build warning which is introduced by
commit ddb5c5be "blackfin: add baudrate to bdinfo".

board.c:235:3: warning: passing argument 1 of 'simple_strtoul' makes pointer from integer without a cast [enabled by default]
include/vsprintf.h:27:7: note: expected 'const char *' but argument is of type 'unsigned int'

This patch ensures we get the baudrate setting before using it.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>