Documentation/x86: Fix title underline length

Fix:

  Documentation/arch/x86/resctrl.rst:577: WARNING: Title underline too short.

Reported-by: Stephen Rothwell <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: Tony Luck <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Ingo Molnar

Documentation/arch/x86/resctrl.rst

@@ -574,7 +574,7 @@ Memory b/w domain is L3 cache.
 	MB:<cache_id0>=bandwidth0;<cache_id1>=bandwidth1;...
 
 Memory bandwidth Allocation specified in MiBps
----------------------------------------------
+----------------------------------------------
 
 Memory bandwidth domain is L3 cache.
 ::