OpenSBI Firmware with Dynamic Information (FW_DYNAMIC)

OpenSBI firmware with dynamic info (FW_DYNAMIC) is a firmware which gets
information about next booting stage (e.g. a bootloader or an OS) and runtime
OpenSBI library options from previous booting stage.

The previous booting stage will pass information to FW_DYNAMIC by creating
struct fw_dynamic_info in memory and passing it's address to FW_DYNAMIC
via a2 register of RISC-V CPU.

A FW_DYNAMIC firmware is particularly useful when the booting stage executed
prior to OpenSBI firmware is capable of loading both the OpenSBI firmware and
the booting stage binary to follow OpenSBI firmware.

FW_DYNAMIC Compilation

A platform can enable FW_DYNAMIC firmware using any of the following methods.

1. Specifying FW_DYNAMIC=y on the top level make command line.
2. Specifying FW_DYNAMIC=y in the target platform config.mk configuration
   file.

The compiled FW_DYNAMIC firmware ELF file is named fw_dynamic.elf. It's
expanded image file is fw_dynamic.bin. Both files are created in the platform
specific build directory under the build/platform//firmware
directory.

FW_DYNAMIC Firmware Configuration Options

The FW_DYNAMIC firmware does not requires any platform specific configuration
parameters because all required information is passed by previous booting stage
at runtime via struct fw_dynamic_info.