x86: fix return for arch_pcie_msi_vectors_allocate()

arch_pcie_msi_vectors_allocate() has a return type of uint8_t.
One of the error path returns -1 which would result in 255
being returned. So fix that by returning 0 instead, as there is
no vector being allocated anyway.

Signed-off-by: Daniel Leung <[email protected]>

Author: dcpleung

arch/x86/core/pcie.c

@@ -260,7 +260,7 @@ uint8_t arch_pcie_msi_vectors_allocate(unsigned int priority,
 		}
 
 		if ((irq == PCIE_CONF_INTR_IRQ_NONE) || (irq == -1)) {
-			return -1;
+			return 0;
 		}
 
 		vector = z_x86_allocate_vector(priority, prev_vector);