minidump: Move minidump_log_init earlier

Move minidump_log_init from late_init to subsys_init, so if a
crash occurs during early stage, we can still get the log through
minidump, useful for debugging.

Change-Id: I51e57491f7f3f262e2c9ecca2a3f3e7783e800f5
Signed-off-by: Huang Yiwei <hyiwei@codeaurora.org>