Documentation: powerclamp: Escape wildcard in cpumask description

kernel test robot reported htmldocs warning:

Documentation/admin-guide/thermal/intel_powerclamp.rst:328: WARNING: Inline emphasis start-string without end-string.

The mistaken asterisk in /proc/irq/*/smp_affinity is rendered as hyperlink
as the result.

Escape the asterisk to fix above warning.

Link: https://lore.kernel.org/linux-doc/202302122247.N4S791c4-lkp@intel.com/
Fixes: ebf51971 ("thermal: intel: powerclamp: Add two module parameters")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/admin-guide/thermal/intel_powerclamp.rst

@@ -326,7 +326,7 @@ Module Parameters
 
 ``cpumask`` (RW)
 	A bit mask of CPUs to inject idle. The format of the bitmask is same as
-	used in other subsystems like in /proc/irq/*/smp_affinity. The mask is
+	used in other subsystems like in /proc/irq/\*/smp_affinity. The mask is
 	comma separated 32 bit groups. Each CPU is one bit. For example for a 256
 	CPU system the full mask is:
 	ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff