Add and use a generic version of devmem_is_allowed()

As part of adding STRICT_DEVMEM support to the RISC-V port, Zong provided an
implementation of devmem_is_allowed() that's exactly the same as the version in
a handful of other ports.  Rather than duplicate code, I've put a generic
version of this in lib/ and used it for the RISC-V port.

* palmer/generic-devmem:
  arm64: Use the generic devmem_is_allowed()
  arm: Use the generic devmem_is_allowed()
  RISC-V: Use the new generic devmem_is_allowed()
  lib: Add a generic version of devmem_is_allowed()

diff --cc arch/arm/Kconfig
Simple merge

diff --cc arch/arm64/Kconfig
Simple merge

diff --cc arch/arm64/include/asm/io.h
Simple merge

diff --cc arch/riscv/Kconfig
Simple merge

diff --cc include/asm-generic/io.h
Simple merge

diff --cc lib/Kconfig
Simple merge

diff --cc lib/Kconfig.debug
Simple merge

diff --cc lib/Makefile
Simple merge