cxgb4: Remove unused cxgb4_l2t_alloc_switching

cxgb4_l2t_alloc_switching() has been unused since it was added in
commit f7502659 ("cxgb4: Add API to alloc l2t entry; also update
existing ones")

Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Link: https://patch.msgid.link/20241013203831.88051-6-linux@treblig.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>