net/mlx5: fix unintentional sign extension on shift of dest_attr->vport.vhca_id

net/mlx5: fix unintentional sign extension on shift of dest_attr->vport.vhca_id

Shifting dest_attr->vport.vhca_id << 16 results in a promotion from an
unsigned 16 bit integer to a 32 bit signed integer, this is then sign
extended to a 64 bit unsigned long on 64 bitarchitectures. If vhca_id is
greater than 0x7fff then this leads to a sign extended result where all
the upper 32 bits of idx are set to 1. Fix this by casting vhca_id
to the same type as idx before performing the shift.

Fixes: 8e2e08a6d1e0 ("net/mlx5: fs, add support for dest vport HWS action")
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Moshe Shemesh <moshe@nvidia.com>
Link: https://patch.msgid.link/20250116181700.96437-1-colin.i.king@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>