bpf: Fix spelling mistake "arithmatic" -> "arithmetic" in test_verifier

There are a couple of spelling mistakes in two literal strings, fix them.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200331100030.41372-1-colin.king@canonical.com

tools/testing/selftests/bpf/verifier/bounds.c

@@ -501,7 +501,7 @@
 	.result = REJECT
 },
 {
-	"bounds check mixed 32bit and 64bit arithmatic. test1",
+	"bounds check mixed 32bit and 64bit arithmetic. test1",
 	.insns = {
 	BPF_MOV64_IMM(BPF_REG_0, 0),
 	BPF_MOV64_IMM(BPF_REG_1, -1),
@@ -520,7 +520,7 @@
 	.result = ACCEPT
 },
 {
-	"bounds check mixed 32bit and 64bit arithmatic. test2",
+	"bounds check mixed 32bit and 64bit arithmetic. test2",
 	.insns = {
 	BPF_MOV64_IMM(BPF_REG_0, 0),
 	BPF_MOV64_IMM(BPF_REG_1, -1),