phy: marvell: mmp3-hsic: Avoid re-casting __iomem

phy: marvell: mmp3-hsic: Avoid re-casting __iomem

__iomem annotated memory must be accessed via dedicated accessors, even
if actual code is correct (accessing the driver data in
mmp3_hsic_phy_init() brings back the __iomem cast), but dropping its
cast (with or without __force) when storing as driver data seems like
less readable code for any future changes.  Instead, add a dedicated
wrapping structure just to hold the pointer without changing the __iomem
cast.  This makes the code explicit, obvious and solves the sparse
warning:

  phy-mmp3-hsic.c:58:31: warning: cast removes address space '__iomem' of expression

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260216110413.159994-5-krzysztof.kozlowski@oss.qualcomm.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>