tracing/filter: fix kernel-doc warnings

Use the 'struct' keyword for a struct's kernel-doc notation and
use the correct function parameter name to eliminate kernel-doc
warnings:

kernel/trace/trace_events_filter.c:136: warning: cannot understand function prototype: 'struct prog_entry '
kerne/trace/trace_events_filter.c:155: warning: Excess function parameter 'when_to_branch' description in 'update_preds'

Also correct some trivial punctuation problems.

Link: https://lkml.kernel.org/r/20230108021238.16398-1-rdunlap@infradead.org

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>