drivers/perf: riscv: Return error for default case

If the upper two bits has an invalid valid (0x1), the event mapping
is not reliable as it returns an uninitialized variable.

Return appropriate value for the default case.

Fixes: f0c9363 ("perf/riscv-sbi: Add platform specific firmware event handling")

Signed-off-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20241212-pmu_event_fixes_v2-v2-2-813e8a4f5962@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: atishp04

drivers/perf/riscv_pmu_sbi.c

@@ -507,7 +507,7 @@ static int pmu_sbi_event_map(struct perf_event *event, u64 *econfig)
 {
 	u32 type = event->attr.type;
 	u64 config = event->attr.config;
-	int ret;
+	int ret = -ENOENT;
 
 	/*
 	 * Ensure we are finished checking standard hardware events for
@@ -551,10 +551,11 @@ static int pmu_sbi_event_map(struct perf_event *event, u64 *econfig)
 			ret = SBI_PMU_EVENT_TYPE_FW << 16 | RISCV_PLAT_FW_EVENT;
 			*econfig = config & RISCV_PMU_PLAT_FW_EVENT_MASK;
 			break;
+		default:
+			break;
 		}
 		break;
 	default:
-		ret = -ENOENT;
 		break;
 	}