media: pci: mgb4: Refactor struct resources

The struct resource end field signifies the end address not the
relative offset from the start field i.e size == (end - start) + 1.

Amend the .end field to specify the end address not the relative size
from the offset as is currently given.

Fixes cocci check:
drivers/media/pci/mgb4/mgb4_regs.c:13:22-25: WARNING: Suspicious code. resource_size is maybe missing with res

Link: https://lore.kernel.org/linux-media/20240429-fix-cocci-v3-1-3c4865f5a4b0@chromium.org
Reviewed-by: Martin Tůma <martin.tuma@digiteqautomotive.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>