efi: Include sys/types.h for register_t

This file depends on sys/types.h being included before it, which isn't
the best assumption. Include it here since we have no namespace
pollution concerns.

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sys/amd64/include/efi.h

@@ -29,6 +29,8 @@
 #ifndef __AMD64_INCLUDE_EFI_H_
 #define __AMD64_INCLUDE_EFI_H_
 
+#include <sys/types.h>
+
 /*
  * XXX: from gcc 6.2 manual:
  * Note, the ms_abi attribute for Microsoft Windows 64-bit targets

sys/arm64/include/efi.h

@@ -35,6 +35,8 @@
 #ifndef __ARM64_INCLUDE_EFI_H_
 #define __ARM64_INCLUDE_EFI_H_
 
+#include <sys/types.h>
+
 #define	EFIABI_ATTR
 
 #ifdef _KERNEL