The patch introduces the alternative configuration of the log buffer for

the lwmon5 board: the storage for the log-buffer itself is OCM(on-chip memory),
the log-buffer header is moved to six GPT registers (PPC440EPX_GPT0_COMP1, ...,
PPC440EPX_GPT0_COMP5).

 To enable this, alternative, configuration the U-Boot board configuration
file for lwmon5 includes the definitions of alternative addresses for header
(CONFIG_ALT_LH_ADDR) and buffer (CONFIG_ALT_LB_ADDR).

 The Linux shall be configured with the CONFIG_ALT_LB_LOCATION option set,
and has the BOARD_ALT_LH_ADDR and BOARD_ALT_LB_ADDR constants defined in the
lwmon5 board-specific header (arch/ppc/platforms/4xx/lwmon5.h).

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>