boards: arm: use QSPI on XIAO BLE Sense

The external flash chip is wired for QSPI. The chip, P25Q16H, has its
"Quad enable" bit in bit 9 of the Read Status Register (section 10.5 in
the datasheet), hence needs this particular quad enable requirement.

Co-authored-by: Marcin Niestroj <m.niestroj@emb.dev>
Signed-off-by: Oleg Ryjkov <oryjkov@gmail.com>