Currently `MCTargetAsmParser::starIsStartOfStatement` checks for `*` at
the start of the statement. There are other (currently) downstream
back-ends that need the same treatment for other tokens. Instead of
introducing bespoke APIs for each such token, we generalize (and rename)
starIsStartOfStatement as tokenIsStartOfStatement which takes the token
of interest as an argument.
Update the BPF AsmParser (the only upstream consumer today) to use the
new version.
d56f23e408