platform/x86: quickstart: Use devm_mutex_init()

platform/x86: quickstart: Use devm_mutex_init()

Use devm_mutex_init() instead of hand-writing it.

This saves some LoC, improves readability and saves some space in the
generated .o file.

Before:
======
   text	   data	    bss	    dec	    hex	filename
   7607	   2616	     64	  10287	   282f	drivers/platform/x86/quickstart.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
   7301	   2544	     64	   9909	   26b5	drivers/platform/x86/quickstart.o

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/530b930c981c436c172c0308b348d4ae4ef72800.1757251867.git.christophe.jaillet@wanadoo.fr
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>