mei: cleanup mei_irq_read_handler

1. Simplify function flow
2. Display errors in error or warnings level instead of debug.
3. Remove excessive debug messages

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --cc drivers/misc/mei/interrupt.c
Simple merge

diff --cc drivers/misc/mei/mei_dev.h
Simple merge