crypto: tcrypt - Fix speed test case for hash to set up sg buffer size equal to payload

Fix speed test case to set up sg buffer size equal to payload.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Gowtham Tammana <g-tammana@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
Reviewed-by: Tero Kristo <kristo@kernel.org>