target/arm: Suppress Coverity warning for PRF

These instructions must perform the sve_access_check, but
since they are implemented as NOPs there is no generated
code to elide when the access check fails.

Fixes: Coverity issues 1393780 & 1393779.
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/translate-sve.c

@@ -5164,7 +5164,7 @@ static bool trans_ST1_zpiz(DisasContext *s, arg_ST1_zpiz *a, uint32_t insn)
 static bool trans_PRF(DisasContext *s, arg_PRF *a, uint32_t insn)
 {
     /* Prefetch is a nop within QEMU.  */
-    sve_access_check(s);
+    (void)sve_access_check(s);
     return true;
 }
 
@@ -5174,7 +5174,7 @@ static bool trans_PRF_rr(DisasContext *s, arg_PRF_rr *a, uint32_t insn)
         return false;
     }
     /* Prefetch is a nop within QEMU.  */
-    sve_access_check(s);
+    (void)sve_access_check(s);
     return true;
 }