eth: fbnic: set FBNIC_QUEUE_RDE_CTL0_EN_HDR_SPLIT on RDE_CTL0

eth: fbnic: set FBNIC_QUEUE_RDE_CTL0_EN_HDR_SPLIT on RDE_CTL0

Fix EN_HDR_SPLIT configuration by writing the field to RDE_CTL0 instead
of RDE_CTL1.

Because drop mode configuration and header splitting enablement both use
RDE_CTL0, we consolidate these configurations into the single function
fbnic_config_drop_mode.

Fixes: 2b30fc01a6c7 ("eth: fbnic: Add support for HDS configuration")
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
Acked-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Link: https://patch.msgid.link/20260211-fbnic-tcp-hds-fixes-v1-1-55d050e6f606@meta.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>