x86: Set resume bit before returning from breakpoint exception

Instruction breakpoints trigger before the instruction executes,
and returning back from the breakpoint handler brings us again
to the instruction that breakpointed. This naturally bring to
a breakpoint recursion.

To solve this, x86 has the Resume Bit trick. When the cpu flags
have the RF flag set, the next instruction won't trigger any
instruction breakpoint, and once this instruction is executed,
RF is cleared back.

This let's us jump back to the instruction that triggered the
breakpoint without recursion.

Use this when an instruction breakpoint triggers.

Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Prasad <[email protected]>
Cc: Mahesh Salgaonkar <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jason Wessel <[email protected]>

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