[syslinux] fix byte ordering problem in TFTP/PXE fs access

[Alexander Wuerstlein]

Hello,

When trying out (g)pxelinux using TFTP URLs and the '<host>::<path>' syntax,
pxelinux seemed to "hang". Some printf debugging and tcpdump revealed that it
looped in the timeout after sending the TFTP RRQ. Further investigation
revealed, that if a plain IP address (e.g. "tftp://12.34.56.78/something") is
used, the byte order is not converted from host to network byte order. When a
hostname is used (e.g. "tftp://server/something"), the resolving function seems
to return the address in the correct byte order.

For a fix, please see the attached patch.