sysutils/linuxfdisk: the port had been further improved (+)

• When printing usage information, give proper references to the programs installed by this port, to avoid possible confusion with similarly named FreeBSD native ones
• Use modern /dev/adaX names for ATA disks in the examples rather than legacy /dev/adX which do not exist since 2015
• Do not hardcode UTIL_LINUX_VERSION, its value is correctly passed on the command line during the build

PR: 257071