spl: atf: add SPL_ATF_NO_PLATFORM_PARAM option

While we expect to call a pointer to a valid FDT (or NULL) as the
platform parameter to an ATF, some ATF versions are not U-Boot aware
and have an insufficiently robust (or an overzealour) parameter
validation: either way, this may cause a hard-stop with uncooperative
ATF versions.

This change adds the option to suppress passing a platform parameter
and will always pass NULL.

Debug output from ATF w/ this option disabled (i.e. default):
      INFO:    plat_param_from_bl2: 0x291450
Debug output from ATF w/ this option enabled:
      INFO:    plat_param_from_bl2: 0

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>