docs: debugfs: Update struct debugfs_reg32 definition

Update the docs to match the implementation, both the definition of
struct debugfs_regset32 and the definition of debugfs_print_regs32().

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20200508212949.2867-1-rikard.falkeborn@gmail.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>