spi: spi-mem: Fix spi_mem_dirmap_destroy() kerneldoc

spi_mem_dirmap_destroy() takes a single argument, remove the @info entry
in the doc.

Fixes: aa167f3f

 ("spi: spi-mem: Add a new API to support direct mapping")
Signed-off-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>