[prim_ram_1p_scr] Simplify nonce input and align to multiples of 64b
[prim_ram_1p_scr] Simplify nonce input and align to multiples of 64b

Signed-off-by: Michael Schaffner <a005a2d3342a687ea2d05360c953107acbe83e08@opentitan.org>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan