nios2: add user_stack_pointer() macro

Follow 5208ba24 ("missing user_stack_pointer() instances")

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
nios2: Install asm-generic trace_clock.h

Follow 8cbd9cc6 ("tracing,x86: Add a TSC trace_clock")

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
nios2: Add ASM_CONST macro

...and use it to define PAGE_SIZE. This way we can define it as UL in C
code and thus get rid of warnings where expressions involving PAGE_SIZE
where converted to unsigned int.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
nios2: Incorporate instruction emulation TLB miss fix from Altera

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>