riscv: define find_{first,next}_zero_bit in asm/bitops.h

These seem to be missing, and trying to build fastboot cmd without
them is causing errors due to these being missing.

Signed-off-by: Maxim Kochetkov <[e-mail]>
Tested-by: E Shattow <[e-mail]
Reviewed-by: Leo Yu-Chi Liang <[e-mail]>

arch/riscv/include/asm/bitops.h

···
 	return k;
 }
 
+static inline int find_next_zero_bit(void *addr, int size, int offset)
+{
+	unsigned long *p = ((unsigned long *)addr) + (offset / BITS_PER_LONG);
+	unsigned long result = offset & ~(BITS_PER_LONG - 1);
+	unsigned long tmp;
+
+	if (offset >= size)
+		return size;
+	size -= result;
+	offset &= (BITS_PER_LONG - 1);
+	if (offset) {
+		tmp = *(p++);
+		tmp |= ~0UL >> (BITS_PER_LONG - offset);
+		if (size < BITS_PER_LONG)
+			goto found_first;
+		if (~tmp)
+			goto found_middle;
+		size -= BITS_PER_LONG;
+		result += BITS_PER_LONG;
+	}
+	while (size & ~(BITS_PER_LONG - 1)) {
+		tmp = *(p++);
+		if (~tmp)
+			goto found_middle;
+		result += BITS_PER_LONG;
+		size -= BITS_PER_LONG;
+	}
+	if (!size)
+		return result;
+	tmp = *p;
+
+found_first:
+	tmp |= ~0UL << size;
+found_middle:
+	return result + ffz(tmp);
+}
+
 /*
  * ffs: find first bit set. This is defined the same way as
  * the libc and compiler builtin ffs routines, therefore
···
 #define hweight32(x) generic_hweight32(x)
 #define hweight16(x) generic_hweight16(x)
 #define hweight8(x) generic_hweight8(x)
+
+#define find_first_zero_bit(addr, size) \
+	find_next_zero_bit((addr), (size), 0)
 
 #define test_and_set_bit		__test_and_set_bit
 #define test_and_clear_bit		__test_and_clear_bit