x86/mce: Fix mce=nobootlog

Since commit

  8b38937b ("x86/mce: Do not enter deferred errors into the generic
		 pool twice")

the mce=nobootlog option has become mostly ineffective (after being only
slightly ineffective before), as the code is taking actions on MCEs left
over from boot when they have a usable address.

Move the check for MCP_DONTLOG a bit outward to make it effective again.

Also, since commit

  011d8261 ("RAS: Add a Corrected Errors Collector")

the two branches of the remaining "if" at the bottom of machine_check_poll()
do same. Unify them.

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200103150722.20313-3-jschoenh@amazon.de