media: renesas: rzg2l-cru: Simplify FIFO empty check

Collapse FIFO empty helper into a single return statement by removing the
redundant `if (amnfifopntr_w == amnfifopntr_r_y) return true;` path. Make
`rzg2l_fifo_empty()` directly return `amnfifopntr_w == amnfifopntr_r_y`
to improve readability without changing behavior.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/aAtQThCibZCROETx@stanley.mountain/


Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Tested-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Link: https://lore.kernel.org/r/20250429091609.9947-2-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>