arm: Only include sysreg.h when needed in asm.h

We only need sysreg.h for armv6 barriers

Sponsored by:	Arm Ltd
Differential Revision:	https://reviews.freebsd.org/D41141

sys/arm/arm/cpufunc_asm.S

@@ -45,6 +45,8 @@
 #include <machine/asm.h>
 __FBSDID("$FreeBSD$");
 
+#include <machine/sysreg.h>
+
 	.text
 	.align	2
 

sys/arm/arm/hypervisor-stub.S

@@ -29,6 +29,7 @@
 #include <machine/asm.h>
 #include <machine/asmacros.h>
 #include <machine/armreg.h>
+#include <machine/sysreg.h>
 
 __FBSDID("$FreeBSD$");
 

sys/arm/include/asm.h

@@ -41,7 +41,6 @@
 #ifndef _MACHINE_ASM_H_
 #define _MACHINE_ASM_H_
 #include <sys/cdefs.h>
-#include <machine/sysreg.h>
 
 #define	_C_LABEL(x)	x
 #define	_ASM_LABEL(x)	x
@@ -194,6 +193,7 @@
 #endif
 
 #elif __ARM_ARCH == 6
+#include <machine/sysreg.h>
 #define ISB	mcr CP15_CP15ISB
 #define DSB	mcr CP15_CP15DSB
 #define DMB	mcr CP15_CP15DMB