iwlwifi: pcie: move iwl_pcie_ctxt_info_alloc_dma() to user

There's no need for this to be an inline in the header file,
only the context-info.c file ever uses it. Move it there.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200418110539.818a06457888.Ib4f55280cd14d7edab37f2992b381c9b6ca4cd7a@changeid