Revert "Convert to/from old EFB scale numbering"

This reverts commit 1fc910b3ea,
replacing the old INI setting EFBScale with a new INI setting
called InternalResolution, which has a simpler mapping:

                  | EFBScale             | InternalResolution
----------------- | -------------------- | --------------------
Auto (fractional) | 0                    |
Auto (integral)   | 1                    | 0
1x                | 2                    | 1
1.5x              | 3                    |
2x                | 4                    | 2
2.5x              | 5                    |
3x                | 6                    | 3
4x                | 7                    | 4
5x                | 8                    | 5
6x                | 9                    | 6

All the fractional IRs were removed in f090a943.

Source/Core/Core/Analytics.cpp

@@ -224,10 +224,10 @@ void DolphinAnalytics::MakePerGameBuilder()
   builder.AddData("cfg-gfx-vsync", g_Config.bVSync);
   builder.AddData("cfg-gfx-aspect-ratio", g_Config.iAspectRatio);
   builder.AddData("cfg-gfx-efb-access", g_Config.bEFBAccessEnable);
-  builder.AddData("cfg-gfx-efb-scale", g_Config.iEFBScale);
   builder.AddData("cfg-gfx-efb-copy-format-changes", g_Config.bEFBEmulateFormatChanges);
   builder.AddData("cfg-gfx-efb-copy-ram", !g_Config.bSkipEFBCopyToRam);
   builder.AddData("cfg-gfx-efb-copy-scaled", g_Config.bCopyEFBScaled);
+  builder.AddData("cfg-gfx-internal-resolution", g_Config.iEFBScale);
   builder.AddData("cfg-gfx-tc-samples", g_Config.iSafeTextureCache_ColorSamples);
   builder.AddData("cfg-gfx-stereo-mode", g_Config.iStereoMode);
   builder.AddData("cfg-gfx-per-pixel-lighting", g_Config.bEnablePixelLighting);