qcom: Don't enable LINUX_KERNEL_IMAGE_HEADER by default

qcom: Don't enable LINUX_KERNEL_IMAGE_HEADER by default

Enabling LINUX_KERNEL_IMAGE_HEADER by default doesn't allow
ENABLE_ARM_SOC_BOOT0_HOOK to work properly on db410c when U-Boot is
loaded as a first stage bootloader. It leads to secondary CPUs bringup
failure and later causing the Linux kernel to freeze.

So fix it via selectively enabling LINUX_KERNEL_IMAGE_HEADER where it's
actually required.

Fixes: 059d526af312 ("mach-snapdragon: generalise board support")
Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>