mvpcie(4): fix panic if "reset-gpios" is not available

[Tobias Heider]

OF_getproplen() will return -1 if "reset-gpios" is not found which
currently causes a panic:

panic: malloc: allocation too large, type = 2, size = 4294967295

Below is a fix.

ok?

Index: mvpcie.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/arch/armv7/marvell/mvpcie.c,v
retrieving revision 1.5
diff -u -p -r1.5 mvpcie.c
--- mvpcie.c    24 Oct 2021 17:52:27 -0000      1.5
+++ mvpcie.c    13 Feb 2022 13:24:17 -0000
@@ -106,7 +106,7 @@ struct mvpcie_port {
        int                      po_fn;
 
        uint32_t                *po_gpio;
-       size_t                   po_gpiolen;
+       int                      po_gpiolen;
 
        struct arm32_pci_chipset po_pc;
        int                      po_bus;
@@ -353,7 +353,7 @@ mvpcie_port_attach(struct mvpcie_softc *
        po->po_bridge_iolimit = 1;
 
        po->po_gpiolen = OF_getproplen(po->po_node, "reset-gpios");
-       if (po->po_gpiolen) {
+       if (po->po_gpiolen > 0) {
                po->po_gpio = malloc(po->po_gpiolen, M_DEVBUF, M_WAITOK);
                OF_getpropintarray(po->po_node, "reset-gpios",
                    po->po_gpio, po->po_gpiolen);