arm64: zynqmp: Add debug messages to bl2_plat_get_bl31_params()

It is useful to get information about BL type and entry address that's why
add some debug messages.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/fb023b618a009009a0b564c24223cadc10ced5b3.1652871741.git.michal.simek@amd.com