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>

drivers/misc/mei/mei_dev.h

@@ -456,6 +456,16 @@ static inline u32 mei_data2slots(size_t length)
 	return DIV_ROUND_UP(sizeof(struct mei_msg_hdr) + length, 4);
 }
 
+/**
+ * mei_slots2data- get data in slots - bytes from slots
+ * @slots -  number of available slots
+ * returns  - number of bytes in slots
+ */
+static inline u32 mei_slots2data(int slots)
+{
+	return slots * 4;
+}
+
 /*
  * mei init function prototypes
  */