PCI: rcar-gen2: Remove duplicated bit-wise or of RCAR_PCI_INT_SIGRETABORT

Bit pattern RCAR_PCI_INT_SIGRETABORT is being bit-wise or'd twice;
remove the redundant 2nd RCAR_PCI_INT_SIGRETABORT.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>