tunable SYSCTL's. Linux module parameters are associated with the
module they belong to. FreeBSD does not share this concept of a parent
module. Instead add macros which define the prefix to use for the
module parameters in the LinuxKPI consumers.
While at it convert all "bool" LinuxKPI module parameters to "byte"
type, because we don't have a "bool" type of SYSCTL in FreeBSD.
Sponsored by: Mellanox Technologies
MFC after: 1 week
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