powerpc: Use shared font data

PowerPC has a 'btext' font used for the console which is almost identical
to the shared font_sun8x16, so use it rather than duplicating the data.

They were actually identical until about a decade ago when
   commit bcfbeece ("drivers: console: font_: Change a glyph from
                        "broken bar" to "vertical line"")

which changed the | in the shared font to be a solid
bar rather than a broken bar.  That's the only difference.

This was originally spotted by the PMF source code analyser, which
noticed that sparc does the same thing with the same data, and they
also share a bunch of functions to manipulate the data.  I've previously
posted a near identical patch for sparc.

Tested very lightly with a boot without FS in qemu.
Signed-off-by: "Dr. David Alan Gilbert" <linux@treblig.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230825142754.1487900-1-linux@treblig.org

arch/powerpc/Kconfig.debug

@@ -147,6 +147,8 @@ config BDI_SWITCH
 config BOOTX_TEXT
 	bool "Support for early boot text console (BootX or OpenFirmware only)"
 	depends on PPC_BOOK3S
+	select FONT_SUN8x16
+	select FONT_SUPPORT
 	help
 	  Say Y here to see progress messages from the boot firmware in text
 	  mode. Requires either BootX or Open Firmware.

lib/fonts/Kconfig

@@ -98,7 +98,7 @@ config FONT_10x18
 
 config FONT_SUN8x16
 	bool "Sparc console 8x16 font"
-	depends on FRAMEBUFFER_CONSOLE && (!SPARC && FONTS || SPARC)
+	depends on (FRAMEBUFFER_CONSOLE && (FONTS || SPARC)) || BOOTX_TEXT
 	help
 	  This is the high resolution console font for Sun machines. Say Y.