Move regexp to global in meminfo_linux.go
Move regexp to global in meminfo_linux.go

Compile regexp outside of parsing function in meminfo_linux.go

Signed-off-by: Shapor Naghibzadeh <5bb56de8e47b8c98d5d151348393d71d6b0b04cb@google.com>

prometheus/node_exporter,siavashs/node_exporter,siavashs/node_exporter,prometheus/node_exporter,prometheus/node_exporter,siavashs/node_exporter,siavashs/node_exporter