firmware: qcom_scm: Use fixed width src vm bitmap

The maximum VMID for assign_mem is 63. Use a u64 to represent this
bitmap instead of architecture-dependent "unsigned int" which varies in
size on 32-bit and 64-bit platforms.

Acked-by: Kalle Valo <kvalo@kernel.org> (ath10k)
Tested-by: Gokul krishna Krishnakumar <quic_gokukris@quicinc.com>
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
Reviewed-by: Bjorn Andersson <andersson@kernel.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230213181832.3489174-1-quic_eberman@quicinc.com