MIPS: Fix ISA I FP sigcontext access violation handling

Complement commit 0ae8dceaebe3 ("Merge with 2.3.10.") and use the local
`fault' handler to recover from FP sigcontext access violation faults,
like corresponding code does in r4k_fpu.S.  The `bad_stack' handler is
in syscall.c and is not suitable here as we want to propagate the error
condition up through the caller rather than killing the thread outright.
Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14474/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/r2300_fpu.S

@@ -21,7 +21,7 @@
 #define EX(a,b)							\
 9:	a,##b;							\
 	.section __ex_table,"a";				\
-	PTR	9b,bad_stack;					\
+	PTR	9b,fault;					\
 	.previous
 
 	.set	noreorder