gdb/testsuite/lib/rocm: Fix with_rocm_gpu_lock

A recent commit refactored with_rocm_gpu_lock:

    commit fbb0edfe
    Date:   Sat May 4 10:41:09 2024 +0200

        [gdb/testsuite] Factor out proc with_lock

        Factor out proc with_lock from with_rocm_gpu_lock, and move required procs
        lock_file_acquire and lock_file_release to lib/gdb-utils.exp.

This causes regressions in gdb.rocm/*.exp (as well as in downstream
rocgdb).  The issue can be reproduced in the following minimal test:

    load_lib rocm.exp
    set foo hello
    with_rocm_gpu_lock {
        verbose -logs $foo
    }

The issue is that the body to execute under the lock is executed in the
context of with_rocm_gpu_lock (uplevel 1 used in with_lock) instead of
in the context of the "original" caller.

This patch adjusted with_rocm_gpu_lock to account for the new extra
frame in the call stack between the caller of with_rocm_gpu_lock and
where the code execution is triggered.

Approved-By: Tom de Vries <tdevries@suse.de>

Change-Id: I79ce2c9615012215867ed5bb60144abe7dce28fe