Fix device tree schema validation error messages for the SiFive
Unmatched: ' cache-sets:0:0: 1024 was expected'.

The existing bindings allow for just 1024 cache-sets but the fu740 on
Unmatched the has 2048 cache-sets. The ISA itself permits any arbitrary
power of two, however this is not supported by dt-schema. The RTL for
the IP, to which the number of cache-sets is a tunable parameter, has
been released publicly so speculatively adding a small number of
"reasonable" values seems unwise also.

Instead, as the binding only supports two distinct controllers: add 2048
and explicitly lock it to the fu740's l2 cache while limiting 1024 to
the l2 cache on the fu540.

Fixes: af951c3a ("dt-bindings: riscv: Update l2 cache DT documentation to add support for SiFive FU740")
Reported-by: Atul Khare <atulkhare@rivosinc.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220803185359.942928-1-mail@conchuod.ieSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>