crypto: omap-aes - move definitions over to a separate header file

Move over most of the omap-aes driver internal definitions to a separate
header file. This is done so that the same definitions can be used in
the upcoming AES-GCM support code.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>