kernel: enable (ARM|ARM64)_MODULE_PLTS in generic config

kernel: enable (ARM|ARM64)_MODULE_PLTS in generic config

This allows loading modules with large memory requirements, recently needed
while testing on armvirt/32. Past forum discussions [1] and bug reports [2]
also raised this and the ipq806x target already set it in response [3].
Given this increases kernel image size by only ~1KB, is generally useful on
multi-platform kernels, and enabled by default on upstream arm32 Linux, add
it to the generic config.

The setting has similar utility on arm64, is a requirement for KASLR, and
already enabled on most OpenWrt aarch64 targets, so pull this into the
top-level generic config.

[1]: https://forum.openwrt.org/t/vmap-allocation-for-size-442368-failed-use-vmalloc-size-to-increase-size/34545/7
[2]: https://github.com/openwrt/openwrt/issues/8282
[3]: f81e148eb6 ("ipq806x: update 4.19 kernel config").

Signed-off-by: Tony Ambardar <itugrok@yahoo.com>