misc: pci_endpoint_test: Remove dead BAR read before doorbell trigger

misc: pci_endpoint_test: Remove dead BAR read before doorbell trigger

The assignment before the writel sequence is dead code (bar is
unconditionally overwritten by the re-read immediately after) so remove the
assignment entirely.

Note that the DB_BAR register is a plain value written by the endpoint
firmware; reading it carries no side effect.

Signed-off-by: Carlos Bilbao (Lambda) <carlos.bilbao@kernel.org>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Koichiro Den <den@valinux.co.jp>
Link: https://patch.msgid.link/20260410230300.135631-3-carlos.bilbao@kernel.org