Add FC-AL-2 IDLEs to state_rx

[bluecmd]

According to FC-AL-2

The Arbitrate Primitive Signal (ARByx) may be transmitted in place of an Idle and therefore becomes a Fill Word which may be removed for clock skew management

A received Ordered Set shall be detected as an Arbitrate Primitive Signal (ARByx) by detecting that its first two characters (fully decoded) are equal to the value shown in table 2, regardless of the value of characters 3 and 4 (y and x). L_Ports shall only
originate an Arbitrate Primitive Signal (ARByx) where y = x. All Arbitrate Primitive Signals shall be treated as Fill Words for clock skew management.

So technically all ARByx are idles as well.

This would help a bit to make sense of things in #52 where ARB(EF) was seen as an idle word.