dt-bindings: fuse: Document R-Car E-FUSE / OTP_MEM

Document support for E-FUSE non-volatile memory accessible through
OTP_MEM on R-Car V4H and V4M.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/436506babe4ce468fda19380d9373470468e3752.1716974502.git.geert+renesas@glider.be