x86/efi: Replace GFP_ATOMIC with GFP_KERNEL in efi_query_variable_store()

x86/efi: Replace GFP_ATOMIC with GFP_KERNEL in efi_query_variable_store()

efi_query_variable_store() does an atomic kzalloc() unnecessarily,
because we can never get this far when called in an atomic context,
namely when nonblocking == 1.

Replace it with GFP_KERNEL.

This was found by the DCNS static analysis tool written by myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20180308080020.22828-7-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>