ftrace: Fix warning using plain integer as NULL & spelling corrections
Changed 0 --> NULL to avoid sparse warning
Corrected spelling mistakes reported by checkpatch.pl
Sparse warning below:
sudo make C=2 CF=-D__CHECK_ENDIAN__ M=kernel/trace
CHECK kernel/trace/ftrace.c
kernel/trace/ftrace.c:3007:24: warning: Using plain integer as NULL pointer
kernel/trace/ftrace.c:4758:37: warning: Using plain integer as NULL pointer
Link: http://lkml.kernel.org/r/20190323183523.GA2244@hari-Inspiron-1545
Signed-off-by: Hariprasad Kelam <hariprasad.kelam@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
