riscv: delay.c:77:17: error: implicit declaration of function 'cpu_relax' [-Werror=implicit-function-declaration]

[Naresh Kamboju]

Regression found on riscv gcc-11 built with defconfig
Following build warnings / errors reported on linux next 20211028.

metadata:
    git_describe: next-20211028
    git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
    git_short_log: 503f375baa99 (\"Add linux-next specific files for 20211028\")
    target_arch: riscv
    toolchain: gcc-11

build error :
--------------
/builds/linux/arch/riscv/lib/delay.c: In function '__delay':
/builds/linux/arch/riscv/lib/delay.c:77:17: error: implicit
declaration of function 'cpu_relax'
[-Werror=implicit-function-declaration]
   77 |                 cpu_relax();
      |                 ^~~~~~~~~
cc1: some warnings being treated as errors
make[2]: *** [/builds/linux/scripts/Makefile.build:288:
arch/riscv/lib/delay.o] Error 1


Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>

build link:
-----------
https://builds.tuxbuild.com/208R1uE0CO13gO5XbrrWlqwau7r/build.log

build config:
-------------
https://builds.tuxbuild.com/208R1uE0CO13gO5XbrrWlqwau7r/config

# To install tuxmake on your system globally
# sudo pip3 install -U tuxmake
tuxmake --runtime podman --target-arch riscv --toolchain gcc-11
--kconfig defconfig

--
Linaro LKFT
https://lkft.linaro.org