MIPS: BCM47xx: Add generic function filling SPROM entries

Handling many SPROM revisions became messy, we have tons of functions
specific to various revision groups which are quite hard to track.
For years there is yet another revision 11 asking for support, but
adding it in current the form would make things even worse.
To resolve this problem let's add new function with table-like entries
that will contain revision bitmask for every SPROM variable.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Cc: Jonas Gorski <jonas.gorski@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/9659/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>