tdf#122221: Bin apparently unnecessary early return

Removing these few lines of code fixes the problem on iOS, and has no
apparent ill effect on macOS. But sure, I didn't check that thoroughly
on macOS, so in case this has a bad effect on macOS after all, need to
reinstate the few lines but make them #ifndef IOS.

(Still passes make check.)

Change-Id: I2380d010ba223a698acfe916fca4580a1502be98
diff --git a/vcl/quartz/salgdicommon.cxx b/vcl/quartz/salgdicommon.cxx
index 333c23c..af70708 100644
--- a/vcl/quartz/salgdicommon.cxx
+++ b/vcl/quartz/salgdicommon.cxx
@@ -587,12 +587,6 @@
                                       const SalBitmap& rSrcBitmap,
                                       const SalBitmap& rAlphaBmp )
{
    if (rTR.mnSrcWidth != rTR.mnDestWidth || rTR.mnSrcHeight != rTR.mnDestHeight)
    {
        // TODO - would be better to scale it by the native code
        return false;
    }

    // An image mask can't have a depth > 8 bits (should be 1 to 8 bits)
    if( rAlphaBmp.GetBitCount() > 8 )
        return false;