samples/bpf: syscall_tp_user: Rename num_progs into nr_tests

samples/bpf: syscall_tp_user: Rename num_progs into nr_tests

[ Upstream commit 0ee352fe0d28015cab161b04d202fa3231c0ba3b ]

The variable name num_progs causes confusion because that variable
really controls the number of rounds the test should be executed.

Rename num_progs into nr_tests for the sake of clarity.

Signed-off-by: Jinghao Jia <jinghao@linux.ibm.com>
Signed-off-by: Ruowen Qin <ruowenq2@illinois.edu>
Signed-off-by: Jinghao Jia <jinghao7@illinois.edu>
Link: https://lore.kernel.org/r/20230917214220.637721-3-jinghao7@illinois.edu
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Stable-dep-of: 9220c3ef6fef ("samples/bpf: syscall_tp_user: Fix array out-of-bound access")
Signed-off-by: Sasha Levin <sashal@kernel.org>