Revert "tracing: Constify string literal data member in struct trace_event_call"

This reverts commit 5c4a141f which is
commit 452f4b31 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I8cad2c8acfdda34b6988a2280612e29171798afa
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>