fpga: kconfig: Rename SPL_FPGA_SUPPORT to SPL_FPGA

fpga: kconfig: Rename SPL_FPGA_SUPPORT to SPL_FPGA

The patch does sed 's/SPL_FPGA_SUPPORT/SPL_FPGA/g' but also fixing Makefile
and zynqmp.c to simplify if/endif logic in zynqmp.c.

This change is mostly done to be able to use CONFIG_IS_ENABLED macro and
obj-$(CONFIG_$(SPL_)FPGA) in Makefile. For them symbols need to be in sync.

And removing one line from Topic Miami boards which is not needed because
symbol is not enabled via Kconfig.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>