The bitreverse helper is almost always built into the kernel,
but in a rare randconfig build it is possible to hit a case
in which it is a loadable module while the atmel-i2c driver
is built-in:
arm-linux-gnueabi-ld: drivers/crypto/atmel-i2c.o: in function `atmel_i2c_checksum':
atmel-i2c.c:(.text+0xa0): undefined reference to `byte_rev_table'