selftests/fpu: Fix debugfs_simple_attr.cocci warning

lib/test_fpu.c:66:0-23: WARNING: test_fpu_fops should be defined with DEFINE_DEBUGFS_ATTRIBUTE

 Use DEFINE_DEBUGFS_ATTRIBUTE rather than DEFINE_SIMPLE_ATTRIBUTE
 for debugfs files.

Semantic patch information:

 Rationale: DEFINE_SIMPLE_ATTRIBUTE + debugfs_create_file()
 imposes some significant overhead as compared to
 DEFINE_DEBUGFS_ATTRIBUTE + debugfs_create_file_unsafe().

In order to protect against file removal races, debugfs files created
via debugfs_create_file() now get wrapped by a struct file_operations
at their opening.

If the original struct file_operations are known to be safe against
removal races by themselves already, the proxy creation may be bypassed
by creating the files through debugfs_create_file_unsafe().

In order to help debugfs users who use the common
DEFINE_SIMPLE_ATTRIBUTE() + debugfs_create_file() idiom to
transition to removal safe struct file_operations, the helper macro
DEFINE_DEBUGFS_ATTRIBUTE() has been introduced.

Thus, the preferred strategy is to use
  DEFINE_DEBUGFS_ATTRIBUTE() + debugfs_create_file_unsafe()
now.

Generated by: scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci

Fixes: 4185b3b9 ("selftests/fpu: Add an FPU selftest")
Signed-off-by: kernel test robot <lkp@intel.com>
Signed-off-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/alpine.DEB.2.22.394.2010251117180.2714@hadrien