arch: remove GENERIC_FIND_FIRST_BIT entirely

arch: remove GENERIC_FIND_FIRST_BIT entirely

In 5.12 cycle we enabled GENERIC_FIND_FIRST_BIT config option for ARM64
and MIPS.  It increased performance and shrunk .text size; and so far I
didn't receive any negative feedback on the change.

https://lore.kernel.org/linux-arch/20210225135700.1381396-1-yury.norov@gmail.com/

Now I think it's a good time to switch all architectures to use
find_{first,last}_bit() unconditionally, and so remove corresponding
config option.

The patch does't introduce functioal changes for arc, arm, arm64, mips,
m68k, s390 and x86, for other architectures I expect improvement both in
performance and .text size.

Link: https://lkml.kernel.org/r/20210814211713.180533-5-yury.norov@gmail.com
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Tested-by: Alexander Lobakin <alobakin@pm.me> (mips)
Reviewed-by: Alexander Lobakin <alobakin@pm.me> (mips)
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Will Deacon <will@kernel.org>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: Alexey Klimov <aklimov@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>