With more stuff being done in PBL regular console support gets more and more
useful. This makes the PBL console independent of DEBUG_LL which is only
meant for early debugging but not regular output.
To use the regular PBL console a board must call pbl_set_putc() which stores
a pointer to the putc function to be used.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>