nvmet: pci-epf: remove NVMET_PCI_EPF_Q_IS_SQ

The flag NVMET_PCI_EPF_Q_IS_SQ is set but never used. Remove it.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>