target/mips32: fix false positive from clang

clang build triggers an error for an uninitialized value of the
variable 'instr'.
This is a false positive, as the macro
 #define MIPS32_CONFIG3_ISA_MASK (3 << MIPS32_CONFIG3_ISA_SHIFT)
guarantees the switch/case already covers all the possible values
with cases 0, 1, 2 and 3.

Silent clang by adding a useless default case to the switch.
While there, fix the indentation of the switch/case accordingly to
OpenOCD coding style.

Change-Id: I0ae316754ce7d091dd8366bf314b8e6ee780e313
Signed-off-by: Antonio Borneo <[email protected]>
Fixes: 7de4b12 ("target/mips32: add cpu info detection")
Reviewed-on: https://review.openocd.org/c/openocd/+/8065
Tested-by: jenkins
Reviewed-by: Oleksij Rempel <[email protected]>

src/target/mips32.c

@@ -1607,17 +1607,18 @@ COMMAND_HANDLER(mips32_handle_cpuinfo_command)
 
 	char *instr;
 	switch ((config3 & MIPS32_CONFIG3_ISA_MASK) >> MIPS32_CONFIG3_ISA_SHIFT) {
-		case 0:
-			instr = "MIPS32";
+	case 0:
+		instr = "MIPS32";
 		break;
-		case 1:
-			instr = "microMIPS";
+	case 1:
+		instr = "microMIPS";
 		break;
-		case 2:
-			instr = "MIPS32 (at reset) and microMIPS";
+	case 2:
+		instr = "MIPS32 (at reset) and microMIPS";
 		break;
-		case 3:
-			instr = "microMIPS (at reset) and MIPS32";
+	case 3:
+	default:
+		instr = "microMIPS (at reset) and MIPS32";
 		break;
 	}