cryptodev: support multiple cipher data-units

cryptodev: support multiple cipher data-units

In cryptography, a block cipher is a deterministic algorithm operating
on fixed-length groups of bits, called blocks.

A block cipher consists of two paired algorithms, one for encryption
and the other for decryption. Both algorithms accept two inputs:
an input block of size n bits and a key of size k bits; and both yield
an n-bit output block. The decryption algorithm is defined to be the
inverse function of the encryption.

For AES standard the block size is 16 bytes.
For AES in XTS mode, the data to be encrypted\decrypted does not have to
be multiple of 16B size, the unit of data is called data-unit.
The data-unit size can be any size in range [16B, 2^24B], so, in this
case, a data stream is divided into N amount of equal data-units and
must be encrypted\decrypted in the same data-unit resolution.

For ABI compatibility reason, the size is limited to 64K (16-bit field).
The new field dataunit_len is inserted in a struct padding hole,
which is only 2 bytes long in 32-bit build.
It could be moved and extended later during an ABI-breakage window.

The current cryptodev API doesn't allow the user to select a specific
data-unit length supported by the devices.
In addition, there is no definition how the IV is detected per data-unit
when single operation includes more than one data-unit.

That causes applications to use single operation per data-unit even though
all the data is continuous in memory what reduces datapath performance.

Add a new feature flag to support multiple data-unit sizes, called
RTE_CRYPTODEV_FF_CIPHER_MULTIPLE_DATA_UNITS.
Add a new field in cipher capability, called dataunit_set,
where the devices can report the range of the supported data-unit sizes.
Add a new cipher transformation field, called dataunit_len, where the user
can select the data-unit length for all the operations.

All the new fields do not change the size of their structures,
by filling some struct padding holes.
They are added as exceptions in the ABI check file libabigail.abignore.

Using a bitmap to report the supported data-unit sizes capability allows
the devices to report a range simply as same as the user to read it
simply. also, thus sizes are usually common and probably will be shared
among different devices.

Signed-off-by: Matan Azrad <matan@nvidia.com>
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Akhil Goyal <gakhil@marvell.com>