[RISCV] Fix comment for Zba tests. NFC.

The comments in the Zba tests were referring to the "bitmanip base"
extension (i.e., the Zbb).  Fix it.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D143534

Author: ptomsich

llvm/test/MC/RISCV/rv32zba-valid.s

@@ -1,4 +1,4 @@
-# With Bitmanip base extension:
+# With Zba extension:
 # RUN: llvm-mc %s -triple=riscv32 -mattr=+zba -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-ASM,CHECK-ASM-AND-OBJ %s
 # RUN: llvm-mc %s -triple=riscv64 -mattr=+zba -show-encoding \

llvm/test/MC/RISCV/rv64zba-valid.s

@@ -1,4 +1,4 @@
-# With Bitmanip base extension:
+# With Zba extension:
 # RUN: llvm-mc %s -triple=riscv64 -mattr=+zba -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-ASM,CHECK-ASM-AND-OBJ %s
 # RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+zba < %s \