x86: queensbay: Move unprotect_spi_flash() to arch_misc_init()

With dm pci conversion, pci config read/write in unprotect_spi_flash()
silently fails as at that time dm pci is not ready and bus enumeration
is not done yet. Actually we don't need to do this in that early phase,
hence we delay this call to arch_misc_init().

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>