arm: Fix unintentional fall throughs in arm.c

This small patch fix some unintentional fall-throughs in
`mve_vector_mem_operand'.

	Backported from mainline
	2020-05-28  Andrea Corallo  <andrea.corallo@arm.com>

gcc/
	* config/arm/arm.c (mve_vector_mem_operand): Fix unwanted
	fall-throughs.

gcc/config/arm/arm.c

@@ -13302,26 +13302,31 @@ mve_vector_mem_operand (machine_mode mode, rtx op, bool strict)
 	    if (abs_hwi (val))
 	      return ((reg_no < LAST_ARM_REGNUM && reg_no != SP_REGNUM)
 		      || (!strict && reg_no >= FIRST_PSEUDO_REGISTER));
+	    return FALSE;
 	  case E_V8HImode:
 	  case E_V8HFmode:
 	    if (abs (val) <= 255)
 	      return ((reg_no < LAST_ARM_REGNUM && reg_no != SP_REGNUM)
 		      || (!strict && reg_no >= FIRST_PSEUDO_REGISTER));
+	    return FALSE;
 	  case E_V8QImode:
 	  case E_V4QImode:
 	    if (abs_hwi (val))
 	      return (reg_no <= LAST_LO_REGNUM
 		      || (!strict && reg_no >= FIRST_PSEUDO_REGISTER));
+	    return FALSE;
 	  case E_V4HImode:
 	  case E_V4HFmode:
 	    if (val % 2 == 0 && abs (val) <= 254)
 	      return (reg_no <= LAST_LO_REGNUM
 		      || (!strict && reg_no >= FIRST_PSEUDO_REGISTER));
+	    return FALSE;
 	  case E_V4SImode:
 	  case E_V4SFmode:
 	    if (val % 4 == 0 && abs (val) <= 508)
 	      return ((reg_no < LAST_ARM_REGNUM && reg_no != SP_REGNUM)
 		      || (!strict && reg_no >= FIRST_PSEUDO_REGISTER));
+	    return FALSE;
 	  case E_V2DImode:
 	  case E_V2DFmode:
 	  case E_TImode: