x86: remove custom switch to main thread function

The original idea of using a custom switch to main thread
function is to make sure the buffer to save floating point
registers are aligned correctly or else exception would be
raised when saving/restoring those registers. Since
the struct of the buffer is defined with alignment hint
to toolchain, the alignment will be enforced by toolchain
as long as the k_thread struct variable is a dedicated,
declared variable. So there is no need for the custom
switch to main thread function anymore.

This also allows the stack usage calculation of
the interrupt stack to function properly as the end of
the interrupt stack is not being used for the dummy
thread anymore.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
2 files changed