powerpc/44x: Declare primary_uic static in uic.c

primary_uic is not used outside uic.c, declare it static.

Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Fixes: e58923ed1437 ("[POWERPC] Add arch/powerpc driver for UIC, PPC4xx interrupt controller")
Signed-off-by: Christophe Leroy <[e-mail]>
Signed-off-by: Madhavan Srinivasan <[e-mail]>
Link: https://patch.msgid.link/0e11233d[e-mail]

arch/powerpc/platforms/44x/uic.c

···
 #define UIC_VR		0x7
 #define UIC_VCR		0x8
 
-struct uic *primary_uic;
+static struct uic *primary_uic;
 
 struct uic {
 	int index;