selftests:breakpoints: Fix Format String Warning in breakpoint_test

selftests:breakpoints: Fix Format String Warning in breakpoint_test

This commit resolves a compiler warning regardingthe
use of non-literal format strings in breakpoint_test.c.

The functions `ksft_test_result_pass` and `ksft_test_result_fail`
were previously called with a variable `msg` directly, which could
potentially lead to format string vulnerabilities.

Changes made:
- Modified the calls to `ksft_test_result_pass` and `ksft_test_result_fail`
by adding a "%s" format specifier. This explicitly declares `msg` as a
string argument, adhering to safer coding practices and resolving
the compiler warning.

This change does not affect the functional behavior of the code but ensures
better code safety and compliance with recommended C programming standards.

The previous warning is "breakpoint_test.c:287:17:
warning: format not a string literal and no format arguments
[-Wformat-security]
  287 |                 ksft_test_result_pass(msg);
      |                 ^~~~~~~~~~~~~~~~~~~~~
breakpoint_test.c:289:17: warning: format not a string literal
and no format arguments [-Wformat-security]
  289 |                 ksft_test_result_fail(msg);
      |    "

Signed-off-by: angquan yu <angquan21@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>