x86/sgx: Fix a W=1 build warning in function comment

x86/sgx: Fix a W=1 build warning in function comment

Building the SGX code with W=1 generates below warning:

  arch/x86/kernel/cpu/sgx/main.c:741: warning: Function parameter or
  struct member 'low' not described in 'sgx_calc_section_metric'
  arch/x86/kernel/cpu/sgx/main.c:741: warning: Function parameter or
  struct member 'high' not described in 'sgx_calc_section_metric'
  ...

The function sgx_calc_section_metric() is a simple helper which is only
used in sgx/main.c.  There's no need to use kernel-doc style comment for
it.

Downgrade to a normal comment.

Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240825080649.145250-1-kai.huang@intel.com