mwifiex: pcie: Drop bogus __refdata annotation

As the Marvell PCIE WiFi-Ex driver does not have any code or data
located in initmem, there is no need to annotate the mwifiex_pcie
structure with __refdata.  Drop the annotation, to avoid suppressing
future section warnings.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201211133835.2970384-1-geert+renesas@glider.be