MIPS: cm: Fix warning if MIPS_CM is disabled

Commit e27fbe16af5c ("MIPS: cm: Detect CM quirks from device tree")
introduced

arch/mips/include/asm/mips-cm.h:119:13: error: ‘mips_cm_update_property’
defined but not used [-Werror=unused-function]

Fix this by making empty function implementation inline

Fixes: e27fbe16af5c ("MIPS: cm: Detect CM quirks from device tree")
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/include/asm/mips-cm.h

···
 #ifdef CONFIG_MIPS_CM
 extern void mips_cm_update_property(void);
 #else
-static void mips_cm_update_property(void) {}
+static inline void mips_cm_update_property(void) {}
 #endif
 
 /**