eco32: ptrace: make user_mode(regs) check UP

Since the pt_regs are saved in exception context, if the psw
is checked there, it should be the pre-exception flags that
should be used.

Otoh, if the pt_regs are checked from the ones in switch_to,
this will be incorrect, so this needs revisiting...

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
eco32: ptrace: add interrupts_enabled macro

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
eco32: asm-offsets: add PT_PC and PT_PSW offsets

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
eco32: add initial page fault handling

Work in progress, error paths missing and other quirks
needs fixing.
The basic functionality is there at least.

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>