Hexagon: append eflags to unknown cpu model string

Running qemu-hexagon with a binary that was compiled for an arch version
unknown by qemu can produce a somewhat confusing message:

  qemu-hexagon: unable to find CPU model 'unknown'

Let's give a bit more info by appending the eflags so that the message
becomes:

  qemu-hexagon: unable to find CPU model 'unknown (0x69)'

Signed-off-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Tested-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <8a8d013cc619b94fd4fb577ae6a8df26cedb972b.1683225804.git.quic_mathbern@quicinc.com>

linux-user/hexagon/target_elf.h

@@ -20,6 +20,9 @@
 
 static inline const char *cpu_get_model(uint32_t eflags)
 {
+    static char buf[32];
+    int err;
+
     /* For now, treat anything newer than v5 as a v73 */
     /* FIXME - Disable instructions that are newer than the specified arch */
     if (eflags == 0x04 ||    /* v5  */
@@ -39,7 +42,9 @@ static inline const char *cpu_get_model(uint32_t eflags)
        ) {
         return "v73";
     }
-    return "unknown";
+
+    err = snprintf(buf, sizeof(buf), "unknown (0x%x)", eflags);
+    return err >= 0 && err < sizeof(buf) ? buf : "unknown";
 }
 
 #endif