Modify the ParserMethod of simm26_b operand type to parseImmediate.
Before that, for the simm26_b operand type, the same ParserMethod
was used as simm26_bl. When using the internal assembler to process
the blockaddress with asm instruction, the wrong blockaddress symbol
would be generated due to the call to the getOrCreateSymbol()
interface.
Active voice may be clearer here, also it's not the test that is preventing the regression:
"This regression test is for ensuring the AsmParser does not use the getOrCreateSymbol interface to create blockaddress symbols."