VMware ESXi SSD on RAID showing as non-ssd

Sure, you can do this.

You can tell ESXi that a particular datastore is comprised of SSDs.

Here's how:
Enabling the SSD option on SSD based disks/LUNs that are not detected as SSD by default (2013188)

You end up having to set a datastore claim rule similar to:

esxcli storage nmp satp rule add --satp SATP_TYPE --device naa.ID --option "enable_ssd"

This is a supported and normal solution. I have to do it for SSD datastores sitting behind HP RAID controllers.

TRIM isn't an issue. If you're using a hardware controller, let things be.

The accepted answer works for vSphere 6 as well, and it works for both local and remote SSD drives either with JBOD or RAID configuration. The additional commands not mentioned in the answer are:

# esxcli storage core claimrule load
# esxcli storage core claimrule run
# esxcli storage core claiming reclaim -d <naa.ID>

Then you can test if you were successful using:

esxcli storage core device list -d <naa.ID> |grep SSD

This should return:

Is SSD: true