MIPS: BCM47xx: Simplify handling SPROM revisions

After the big SPROM cleanup moving code to the bcm47xx_sprom_fill_auto
we ended up with few tiny functions, two of them being identical. Let's
get rid of these [12]-liners.
This also stops extracting higher SPROM revisions as revision 1. Now we
have that function nicely handling revisions we don't need it.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: https://patchwork.linux-mips.org/patch/10569/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>