Yes, funds can be transferred from your RRSP to your FHSA. These transfers can be requested using CRA form RC720 Transfer from your RRSP to your FHSA.
Transfers from your RRSP into your FHSA are not tax deductible, even though they use up contribution room. This is not considered to be an RRSP de-registration. No taxes will be withheld.
Funds can also be transferred from an RRSP Spousal where you are the annuitant, and no contributions were made to the RRSP Spousal in the last two years.
A T4FHSA will be issued for this transaction.