PCI: rockchip: Fix rockchip_pcie_ep_assert_intx() bitwise operations

Currently the bitwise operations on the u16 variable 'status' with
the setting ROCKCHIP_PCIE_EP_CMD_STATUS_IS are incorrect because
ROCKCHIP_PCIE_EP_CMD_STATUS_IS is 1UL<<19 which is wider than the
u16 variable.

Fix this by making status a u32.

Fixes: cf590b07 ("PCI: rockchip: Add EP driver for Rockchip PCIe controller")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Acked-by: Shawn Lin <shawn.lin@rock-chips.com>