docs, kprobes: Add riscv as supported architecture

Support of kprobes and kretprobes for riscv was introduced 3 years ago
by the following change:

commit c22b0bcb1dd0 ("riscv: Add kprobes supported")

Add riscv to the list of supported architectures.

Signed-off-by: Ivan Orlov <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/trace/kprobes.rst

···
 - s390
 - parisc
 - loongarch
+- riscv
 
 Configuring Kprobes
 ===================