selftests/bpf: Change test_uretprobe_regs_change for uprobe and uretprobe

selftests/bpf: Change test_uretprobe_regs_change for uprobe and uretprobe

Changing the test_uretprobe_regs_change test to test both uprobe
and uretprobe by adding entry consumer handler to the testmod
and making it to change one of the registers.

Making sure that changed values both uprobe and uretprobe handlers
propagate to the user space.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20250720112133.244369-20-jolsa@kernel.org