crypto: omap-sham - fix digcnt register handling with export/import

[ Upstream commit 3faf757bad75f3fc1b2736f0431e295a073a7423 ]

Running export/import for hashes in peculiar order (mostly done by
openssl) can mess up the internal book keeping of the OMAP SHA core.
Fix by forcibly writing the correct DIGCNT back to hardware. This issue
was noticed while transitioning to openssl 1.1 support.

Fixes: 0d373d60 ("crypto: omap-sham - Add OMAP4/AM33XX SHAM Support")
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>