efi: Make const array 'apple' static

Don't populate the const read-only array 'buf' on the stack but instead
make it static. Makes the object code smaller by 64 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
   9264	      1	     16	   9281	   2441	arch/x86/boot/compressed/eboot.o

After:
   text	   data	    bss	    dec	    hex	filename
   9200	      1	     16	   9217	   2401	arch/x86/boot/compressed/eboot.o

(GCC version 7.2.0 x86_64)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20180308080020.22828-13-ard.biesheuvel@linaro.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/boot/compressed/eboot.c

@@ -423,7 +423,7 @@ static void retrieve_apple_device_properties(struct boot_params *boot_params)
 
 static void setup_quirks(struct boot_params *boot_params)
 {
-	efi_char16_t const apple[] = { 'A', 'p', 'p', 'l', 'e', 0 };
+	static efi_char16_t const apple[] = { 'A', 'p', 'p', 'l', 'e', 0 };
 	efi_char16_t *fw_vendor = (efi_char16_t *)(unsigned long)
 		efi_table_attr(efi_system_table, fw_vendor, sys_table);