efivar-types.h: fix alignment of efi_guid_t

The current alignment of 1 can lead to a lot of Walign-mismatch warnings
in C++. This behavior also doesn't seem to be up to spec, as evidenced
by a similar change made in the Linux ARM kernel:

https://patchwork.kernel.org/project/linux-arm-kernel/patch/20190108152829.11579-1-ard.biesheuvel@linaro.org/

Author: meator

src/include/efivar/efivar-types.h

@@ -20,7 +20,7 @@ typedef struct {
 	uint16_t	c;
 	uint16_t	d;
 	uint8_t		e[6];
-} efi_guid_t __attribute__((__aligned__(1)));
+} efi_guid_t __attribute__((__aligned__(4)));
 
 #if BYTE_ORDER == LITTLE_ENDIAN
 #define EFI_GUID(a,b,c,d,e0,e1,e2,e3,e4,e5) \