perf header: Fail on write_padded error

perf header: Fail on write_padded error

Do not proceed if write_padded() error failed.

Also, add comments to remind that the return value of write_* functions
in util/header.c is an errno code and not the number of bytes written.

Signed-off-by: David Carrillo-Cisneros <[email protected]>
Acked-by: David Ahern <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: He Kuang <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Turner <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Simon Que <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Wang Nan <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>