amd64: make efi_boot global

Reviewed by:	markj
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D31121

sys/amd64/amd64/machdep.c

@@ -222,6 +222,8 @@ struct mtx dt_lock;	/* lock for GDT and LDT */
 
 void (*vmm_resume_p)(void);
 
+bool efi_boot;
+
 static void
 cpu_startup(dummy)
 	void *dummy;
@@ -1604,7 +1606,6 @@ hammer_time(u_int64_t modulep, u_int64_t physfree)
 	struct region_descriptor r_gdt;
 	size_t kstack0_sz;
 	int late_console;
-	bool efi_boot;
 
 	TSRAW(&thread0, TS_ENTER, __func__, NULL);
 

sys/amd64/include/md_var.h

@@ -55,6 +55,8 @@ extern int la57;
  */
 extern char kernphys[];
 
+extern bool efi_boot;
+
 struct	savefpu;
 struct	sysentvec;