drm/msm/msm_drv: Make '_msm_ioremap()' static

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/msm/msm_drv.c:124:15: warning: no previous prototype for ‘_msm_ioremap’ [-Wmissing-prototypes]

Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: linux-arm-msm@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: freedreno@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/msm_drv.c

@@ -121,8 +121,8 @@ struct clk *msm_clk_get(struct platform_device *pdev, const char *name)
 	return clk;
 }
 
-void __iomem *_msm_ioremap(struct platform_device *pdev, const char *name,
-			   const char *dbgname, bool quiet)
+static void __iomem *_msm_ioremap(struct platform_device *pdev, const char *name,
+				  const char *dbgname, bool quiet)
 {
 	struct resource *res;
 	unsigned long size;