Documentation/rtla: Add -A/--aligned option

Cover the newly added -A/--aligned option that aligns timerlat threads
using the corresponding feature of the timerlat tracer.

A note is added to clarify what alignment means, similar to the note in
the tracer implementation in commit 4245bf4dc5 ("tracing/osnoise: Add
option to align tlat threads").

Link: https://lore.kernel.org/r/20260527144928.2944472-3-tglozar@redhat.com
[ remove spurious newline ]
Signed-off-by: Tomas Glozar <tglozar@redhat.com>

Documentation/tools/rtla/common_timerlat_options.txt

@@ -95,3 +95,14 @@
         * **full**        Print the entire stack trace, including unknown addresses.
 
         For unknown addresses, the raw pointer is printed.
+
+**-A**, **--aligned** *us*
+
+        Align wake-up of timerlat threads to a set offset in microseconds.
+
+        The alignment will be applied when the threads wake up at the start of tracing while
+        the timer for the first cycle is armed. Each thread sets its timer to the wake-up time
+        of the previous thread plus the alignment.
+
+        This option may be used with any non-negative argument, including zero, which will
+        align threads so that they wake up all at the same time.