tools: mark 'test_vmalloc.sh' executable

Several of these scripts have come in as old-fashioned patches, and in
the process lost the executable bit.  In most cases it doesn't matter,
since the test infrastructure will explicitly execute them using the
proper shell interpreter, but at least in the case of the new vmalloc
test, the lack of execurable bit caused the test to fail with

    ./run_vmtests: line 217: ./test_vmalloc.sh: Permission denied

because of the lacking exectuable permissions bit.

This patch fixes that up.

NOTE! A simple script to look for non-executable scripts in the kernel,
something like

    git ls-files --stage -- '*.sh' |
        grep 100644 |
        cut -f2 |
        xargs grep -l '#!'

will show that there's a lot of other files that _look_ like executable
shell scripts, but don't have the executable bit set.  I considered just
scripting them all to be executable, but since it looks like the common
pattern is to not really require it, I'm just doing the minimal fix as
pointed out by the kernel test robot.

Fixes: a05ef00c ("selftests/vm: add script helper for CONFIG_TEST_VMALLOC_MODULE")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>