app/testpmd: fix global variable multiple definitions

app/testpmd: fix global variable multiple definitions

Some flow config related global variables are defined in a header file
which was causing multiple definitions of the variables, fixed it by
moving them to the .c file.

Issue has been detected by '-fno-common' gcc flag.

Also while being there,
removed duplicated 'ACTION_RAW_ENCAP_MAX_DAT definition,
moved 'vxlan_encap_conf' & 'nvgre_encap_conf' initialization to
  'cmdline_flow.c' which is better location than 'testpmd.c'
relocated 'action_raw_encap_data' & 'action_raw_decap_data' struct
   definitions slightly within the file

Fixes: 1960be7d32f8 ("app/testpmd: add VXLAN encap/decap")
Fixes: dcd962fc6b4e ("app/testpmd: add NVGRE encap/decap")
Fixes: a1191d39cb57 ("app/testpmd: add MPLSoUDP encapsulation")
Fixes: 3e77031be855 ("app/testpmd: add MPLSoGRE encapsulation")
Cc: stable@dpdk.org
Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>