POST: replace the LOGBUFF_INITIALIZED flag in gd->post_log_word (1 << 31) with...

POST: replace the LOGBUFF_INITIALIZED flag in gd->post_log_word (1 << 31) with the GD_FLG_LOGINIT flag in gd->flags.

This way we become able to utilize the full post_log_word for POST
activities (overwise, POST ECC, which has 0x8000 ID, could be
erroneously treated as started in post_output_backlog() even if there
was actually no POST ECC run (because of OCM POST failure, for
example).

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