mfi.4, mrsas.4: document how to get ATA TRIM support for SSD

while using LSI RAID adapters as it was completely obscure before:
mfi has no TRIM support at all and mrsas provides TRIM
if underlying adapter does it (for Non-RAID drives generally).

share/man/man4/mfi.4

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 15, 2013
+.Dd March 13, 2019
 .Dt MFI 4
 .Os
 .Sh NAME
@@ -84,6 +84,12 @@ then the driver will reduce its probe priority to allow
 .Cd mrsas
 to attach to the card instead of
 .Nm .
+.Pp
+.Nm
+does not provide ATA TRIM support.
+Refer to
+.Cd mrsas
+if TRIM support is required.
 .Sh HARDWARE
 The
 .Nm

share/man/man4/mrsas.4

@@ -34,7 +34,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 8, 2014
+.Dd Mar 13, 2019
 .Dt MRSAS 4
 .Os
 .Sh NAME
@@ -117,6 +117,12 @@ at probe call for device id's 0x005B, 0x005D, and
 0x005F so that
 .Nm
 does not take control of these devices without user intervention.
+.Pp
+Solid-state drives (SSD) get ATA TRIM support with
+.Nm
+if underlying adapter allows it.
+This may require configuring SSD as Non-RAID drive
+rather then JBOD virtual mode.
 .Sh HARDWARE
 The
 .Nm