lib: Simple bitmap library

We add simple bitmap library which will help us create and maintain
bitmaps. It will also help us create a simple HART mask library.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>

lib/sbi/objects.mk

@@ -12,6 +12,7 @@ libsbi-objs-y += riscv_atomic.o
 libsbi-objs-y += riscv_hardfp.o
 libsbi-objs-y += riscv_locks.o
 
+libsbi-objs-y += sbi_bitmap.o
 libsbi-objs-y += sbi_bitops.o
 libsbi-objs-y += sbi_console.o
 libsbi-objs-y += sbi_ecall.o