xfs: remove unused event xfs_pagecache_inval

When the function xfs_flushinval_pages() was removed, it removed the only
caller to the trace event xfs_pagecache_inval. As trace events can take up
to 5K of memory in text and meta data each regardless if they are used or
not, they should not be created when unused. Remove the unused event.

Fixes: fb595814 ("xfs: remove xfs_flushinval_pages")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>