samples: bpf: Update outdated error message

Currently, under samples, several methods are being used to load bpf
program.

Since using libbpf is preferred solution, lots of previously used
'load_bpf_file' from bpf_load are replaced with 'bpf_prog_load_xattr'
from libbpf.

But some of the error messages still show up as 'load_bpf_file' instead
of 'bpf_prog_load_xattr'.

This commit fixes outdated errror messages under samples and fixes some
code style issues.
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191107005153.31541-2-danieltimlee@gmail.com

samples/bpf/hbm.c

@@ -147,7 +147,7 @@ static int prog_load(char *prog)
 	}
 
 	if (ret) {
-		printf("ERROR: load_bpf_file failed for: %s\n", prog);
+		printf("ERROR: bpf_prog_load_xattr failed for: %s\n", prog);
 		printf("  Output from verifier:\n%s\n------\n", bpf_log_buf);
 		ret = -1;
 	} else {

samples/bpf/xdp1_user.c

@@ -139,7 +139,7 @@ int main(int argc, char **argv)
 	map_fd = bpf_map__fd(map);
 
 	if (!prog_fd) {
-		printf("load_bpf_file: %s\n", strerror(errno));
+		printf("bpf_prog_load_xattr: %s\n", strerror(errno));
 		return 1;
 	}
 

samples/bpf/xdp_rxq_info_user.c

@@ -499,7 +499,7 @@ int main(int argc, char **argv)
 	map_fd = bpf_map__fd(map);
 
 	if (!prog_fd) {
-		fprintf(stderr, "ERR: load_bpf_file: %s\n", strerror(errno));
+		fprintf(stderr, "ERR: bpf_prog_load_xattr: %s\n", strerror(errno));
 		return EXIT_FAIL;
 	}
 

samples/bpf/xdp_sample_pkts_user.c

@@ -150,7 +150,7 @@ int main(int argc, char **argv)
 		return 1;
 
 	if (!prog_fd) {
-		printf("load_bpf_file: %s\n", strerror(errno));
+		printf("bpf_prog_load_xattr: %s\n", strerror(errno));
 		return 1;
 	}
 

samples/bpf/xdp_tx_iptunnel_user.c

@@ -268,7 +268,7 @@ int main(int argc, char **argv)
 		return 1;
 
 	if (!prog_fd) {
-		printf("load_bpf_file: %s\n", strerror(errno));
+		printf("bpf_prog_load_xattr: %s\n", strerror(errno));
 		return 1;
 	}