crypto: qat - relocate bank state helper functions

crypto: qat - relocate bank state helper functions

The existing implementation of bank state management functions,
including saving and restoring state, is located within 4xxx device
files. However, these functions do not contain GEN4-specific code and
are applicable to other QAT generations.

Relocate the bank state management functions to a new file,
adf_bank_state.c, and rename them removing the `gen4` prefix. This change
enables the reuse of such functions across different QAT generations.

Add documentation to bank state related functions that were
moved from QAT 4xxx specific files to common files.

This does not introduce any functional change.

Signed-off-by: Małgorzata Mielnik <malgorzata.mielnik@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>