net sched actions: fix sparse warning

The variable _data in include/asm-generic/sections.h defines sections,
this causes sparse warning in pedit:

net/sched/act_pedit.c:293:35: warning: symbol '_data' shadows an earlier one
./include/asm-generic/sections.h:36:13: originally declared here

Therefore rename the variable.

Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Roman Mashak <mrv@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>