[ARM] Remove rt_sigframe puc and pinfo pointers

These two members appear to be surplus to requirements.  Discussing
this issue with glibc folk:

| > Additionally, do you see any need for these weird "puc" and "pinfo"
| > pointers in the kernels rt_sigframe structure?  Can we kill them?
|
| We can kill them.  I checked with Phil B. about them last week, and he
| didn't remember any reason they still needed to be there.  And nothing
| should know where they are on the stack.  Unfortunately, doing this
| will upset GDB, which knows that the saved registers are 0x88 bytes
| above the stack pointer on entrance to an rt signal trampoline; but,
| since puc and pinfo are quite recognizable, I can adapt GDB to support
| the new layout if you want to remove them.

So remove them.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>