samples: pktgen: correct dev to DEV

In the pktgen_sample01_simple.sh script, the device variable is uppercase
'DEV' instead of lowercase 'dev'. Because of this typo, the script cannot
enable UDP tx checksum.

Fixes: 460a9aa ("samples: pktgen: add UDP tx checksum support")
Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Link: https://patch.msgid.link/20241112030347.1849335-1-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Wei Fang

samples/pktgen/pktgen_sample01_simple.sh

@@ -76,7 +76,7 @@ if [ -n "$DST_PORT" ]; then
     pg_set $DEV "udp_dst_max $UDP_DST_MAX"
 fi
 
-[ ! -z "$UDP_CSUM" ] && pg_set $dev "flag UDPCSUM"
+[ ! -z "$UDP_CSUM" ] && pg_set $DEV "flag UDPCSUM"
 
 # Setup random UDP port src range
 pg_set $DEV "flag UDPSRC_RND"