* include: Introduce elf64.h and elf.h
Added elf64.h for 64bit ELF support and moved common definitions
from elf32.h to elf.h. Also introduced Elf_xxx to be used in
common libraries such as binfmt.
* binfmt, include, modlib, module: Add support for ELF64
Elf_xxx must be used instead of Elf32_xxx to support ELF64.
To use ELF64, CONFIG_ELF_64BIT must be enabled.
* binfmt, modlib: Add support for relocate address
* arch: risc-v: Add include/elf.h
* libs: machine: Add risc-v related files.
NOTE: Currently only supports ELF64
* boards: maix-bit: Add elf and posix_spawn configurations
* boards: maix-bit: Add support for module configuration
* arch: risc-v: Remove unused typedef for irqstate_t
NOTE: irqstate_t is defined in arch/risc-v/include/types.h
* arch: risc-v: Add typedef irqstate_t for __LP64__
* arch: risc-v: Add SMP support to K210 (RV64GC) processor
* boards: maxi-bit: Update READMEs and add smp/defconfig
Author: Gregory Nutt <gnutt@nuttx.org>
Run all .c and .h modified in PR through nxstyle.
Author: Masayuki Ishikawa <masayuki.ishikawa@gmail.com>
feature k210 (#16)
* arch: risc-v: Add support for __LP64__ to types.h
* arch: risc-v: Add support for RV64GC to common files
* arch: risc-v: Add support for Kendryte K210 processor (RV64GC)
* boards: risk-v: Add support for Sipeed Maix Bit with K210
* tools: Add support for Kendryte K210 processor
