perf: cast (struct timeval).tv_sec when printing

The musl-libc [1] defines (struct timeval).tv_sec as a
'long long' for arm and other architectures. The default
build having a '-Wformat' flag, not casting the field
when printing prevents from building perf.

This patch casts the (struct timeval).tv_sec fields to the
expected format.

[1] git://git.musl-libc.org/musl



Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>