net: mana: Use at least SZ_4K in doorbell ID range check

net: mana: Use at least SZ_4K in doorbell ID range check

mana_gd_ring_doorbell() accesses offsets up to DOORBELL_OFFSET_EQ
(0xFF8) + 8 bytes = 4KB within each doorbell page. A db_page_size
smaller than SZ_4K is fundamentally incompatible with the driver:
doorbell pages would overlap and the device cannot function correctly.

Validate db_page_size at the source and fail the
probe early if the value is below SZ_4K. This ensures the doorbell ID
range check in mana_gd_register_device() can rely on db_page_size
being valid.

Fixes: 89fe91c65992 ("net: mana: hardening: Validate doorbell ID from GDMA_REGISTER_DEVICE response")
Signed-off-by: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260325180423.1923060-1-ernis@linux.microsoft.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>