tools bitmap: Add missing asm-generic/bitsperlong.h include

small_const_nbits is defined in asm-generic/bitsperlong.h which
bitmap.h uses but doesn't include causing build failures in some build
systems. Add the missing #include.

Note the bitmap.h in tools has diverged from that of the kernel, so no
changes are made there.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: André Almeida <andrealmeid@igalia.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Darren Hart <dvhart@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Ido Schimmel <idosch@nvidia.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jason Xing <kerneljasonxing@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Jonas Gottlieb <jonas.gottlieb@stackit.cloud>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Maurice Lambert <mauricelambert434@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Machata <petrm@nvidia.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yuyang Huang <yuyanghuang@google.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>