efi_loader: QEMU CONFIG_EFI_GRUB_ARM32_WORKAROUND=n

CONFIG_EFI_GRUB_ARM32 is only needed for architectures with caches that are
not managed via CP15 (or for some outdated buggy versions of GRUB). It
makes more sense to disable the setting per architecture than per defconfig.

Move QEMU's CONFIG_EFI_GRUB_ARM32_WORKAROUND=n from defconfig to Kconfig.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>