Revert "riscv64: enable V."

This reverts commit aa204ec49cb14ef0c9f8f5cf472295653d9fd4a0.

Reason for revert: b/300158981

Change-Id: I4e969c7fccade0f8e1b29cb6267c27355ddca866
diff --git a/cc/config/riscv64_device.go b/cc/config/riscv64_device.go
index e048622..40919c0 100644
--- a/cc/config/riscv64_device.go
+++ b/cc/config/riscv64_device.go
@@ -26,14 +26,14 @@
 		// Help catch common 32/64-bit errors.
 		"-Werror=implicit-function-declaration",
 		"-fno-emulated-tls",
-		"-march=rv64gcv_zba_zbb_zbs",
+		"-march=rv64gc_zba_zbb_zbs",
 	}
 
 	riscv64ArchVariantCflags = map[string][]string{}
 
 	riscv64Ldflags = []string{
 		"-Wl,--hash-style=gnu",
-		"-march=rv64gcv_zba_zbb_zbs",
+		"-march=rv64gc_zba_zbb_zbs",
 	}
 
 	riscv64Lldflags = append(riscv64Ldflags,