patch check_cond abstraction, now works properly with thumb and arm

src/crab/arm/arm.cr

@@ -5,7 +5,7 @@
 
 module ARM
   def arm_execute(instr : Word) : Nil
-    if check_cond instr
+    if check_cond bits(instr, 28..31)
       hash = hash_instr instr
       lut[hash].call instr
     else

src/crab/cpu.cr

@@ -62,7 +62,7 @@ class CPU
   end
 
   def check_cond(cond : Word) : Bool
-    case bits cond, 28..31
+    case cond
     when 0x0 then @cpsr.zero
     when 0x1 then !@cpsr.zero
     when 0x2 then @cpsr.carry