include: net: Simplify the usage of __always_inline

Since commit de4d2e9e (" bitops: Add fls_long and __ffs64")
<linux/compiler.h> is included in include/linux/bitops.h,
which allows us to marking a function as 'always_inline' in a simpler
format.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>