The number of register fields cannot be assumed to be ALE_FIELDS_MAX
as some platforms can have lesser fields.

Solve this by embedding the actual number of fields available
in platform data and use that instead of ALE_FIELDS_MAX.

Gets rid of the below warning on BeagleBone Black

[    1.007735] WARNING: CPU: 0 PID: 33 at drivers/base/regmap/regmap.c:1208 regmap_field_init+0x88/0x9c
[    1.007802] invalid empty mask defined
[    1.007812] Modules linked in:
[    1.007842] CPU: 0 UID: 0 PID: 33 Comm: kworker/u4:3 Not tainted 6.11.0-01459-g508403ab7b74-dirty #840
[    1.007867] Hardware name: Generic AM33XX (Flattened Device Tree)
[    1.007890] Workqueue: events_unbound deferred_probe_work_func
[    1.007935] Call trace:
[    1.007957]  unwind_backtrace from show_stack+0x10/0x14
[    1.007999]  show_stack from dump_stack_lvl+0x50/0x64
[    1.008033]  dump_stack_lvl from __warn+0x70/0x124
[    1.008077]  __warn from warn_slowpath_fmt+0x194/0x1a8
[    1.008113]  warn_slowpath_fmt from regmap_field_init+0x88/0x9c
[    1.008154]  regmap_field_init from devm_regmap_field_alloc+0x48/0x64
[    1.008193]  devm_regmap_field_alloc from cpsw_ale_create+0xfc/0x320
[    1.008251]  cpsw_ale_create from cpsw_init_common+0x214/0x354
[    1.008286]  cpsw_init_common from cpsw_probe+0x4ac/0xb88
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Closes: https://lore.kernel.org/netdev/CAMuHMdUf-tKRDzkz2_m8qdFTFutefddU0NTratVrEjRTzA3yQQ@mail.gmail.com/
Fixes: 11cbcfea ("net: ethernet: ti: cpsw_ale: use regfields for number of Entries and Policers")
Signed-off-by: Roger Quadros <rogerq@kernel.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240924-am65-cpsw-multi-rx-fix-v1-1-0ca3fa9a1398@kernel.orgSigned-off-by: Paolo Abeni <pabeni@redhat.com>