Bugfixes in sl, cos_kernel_api and kernel

[phanikishoreg]

Summary of this Pull Request (PR)

• sl:
  1. sl_thd_block was broken because it was trying to set a timeout for a non-timeout block.
  2. sl_cs_exit_schedule_nospin_arg should be able to schedule a thread that is in SL_THD_WOKEN state.
• kernel: tcap_next should be set to current tcap for switching to scheduler in cos_sched_asnd case.
• cos_kernel_api: cos_switch bit packing fix: packing higher order 16bits from 48bit tcap_prio_t into higher order 16bits of arg3 to call_cap_op.

Intent for your PR

Choose one (Mandatory):

• [ ] This PR is for a code-review and is intended to get feedback, but not to be pulled yet.
• [x] This PR is mature, and ready to be integrated into the repo.

Reviewers (Mandatory):

@gparmer

Code Quality

As part of this pull request, I've considered the following:

Style:

• [x] Comments adhere to the Style Guide (SG)
• [x] Spacing adhere's to the SG
• [x] Naming adhere's to the SG
• [x] All other aspects of the SG are adhered to, or exceptions are justified in this pull request
• [ ] I have run the auto formatter on my code before submitting this PR (see doc/auto_formatter.md for instructions)

Code Craftsmanship:

• [x] I've made an attempt to remove all redundant code
• [x] I've considered ways in which my changes might impact existing code, and cleaned it up
• [x] I've formatted the code in an effort to make it easier to read (proper error handling, function use, etc...)
• [x] I've commented appropriately where code is tricky
• [x] I agree that there is no "throw-away" code, and that code in this PR is of high quality

Testing

I've tested the code using the following test programs (provide list here):

• vkernel, micro booter, unit_schedtests, unit_defci, unit_cxx, llbooter_test