Explicitly depend on icp module in initramfs hook

Automatic dependency resolution is unreliable on many systems.
Follow suit with existing code, and explicitly include icp
in module dependencies.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Antonio Russo <antonio.e.russo@gmail.com>
Closes #6751

contrib/initramfs/hooks/zfs

@@ -19,7 +19,7 @@ COPY_EXEC_LIST="$COPY_EXEC_LIST /bin/hostname /sbin/blkid"
 
 # Explicitly specify all kernel modules because automatic dependency resolution
 # is unreliable on many systems.
-BASE_MODULES="zlib_deflate spl zavl zcommon znvpair zunicode zfs"
+BASE_MODULES="zlib_deflate spl zavl zcommon znvpair zunicode zfs icp"
 CRPT_MODULES="sun-ccm sun-gcm sun-ctr"
 MANUAL_ADD_MODULES_LIST="$BASE_MODULES"