trace: Add __print_ns_to_secs() and __print_ns_without_secs() helpers

To have nanosecond output displayed in a more human readable format, its
nicer to convert it to a seconds format (XXX.YYYYYYYYY). The problem is that
to do so, the numbers must be divided by NSEC_PER_SEC, and moded too. But as
these numbers are 64 bit, this can not be done simply with '/' and '%'
operators, but must use do_div() instead.

Instead of performing the expensive do_div() in the hot path of the
tracepoint, it is more efficient to perform it during the output phase. But
passing in do_div() can confuse the parser, and do_div() doesn't work
exactly like a normal C function. It modifies the number in place, and we
don't want to modify the actual values in the ring buffer.

Two helper functions are now created:

  __print_ns_to_secs() and __print_ns_without_secs()

They both take a value of nanoseconds, and the former will return that
number divided by NSEC_PER_SEC, and the latter will mod it with NSEC_PER_SEC
giving a way to print a nice human readable format:

 __print_fmt("time=%llu.%09u",
	__print_ns_to_secs(REC->nsec_val),
	__print_ns_without_secs(REC->nsec_val))

Link: https://lkml.kernel.org/r/e503b903045496c4ccde52843e1e318b422f7a56.1624372313.git.bristot@redhat.com

Cc: Phil Auld <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Kate Carcia <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Alexandre Chartre <[email protected]>
Cc: Clark Willaims <[email protected]>
Cc: John Kacur <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Steven Rostedt <[email protected]>
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

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