bn: Drop unnecessary use of r9
This is done in other versions due to the possibility of an early
return.  However, there is no early return here.
@@ -72,8 +72,6 @@ my $np = "r6";
my $n0 = "r7";
my $num = "r8";
-$rp = "r9"; # $rp is reassigned
-
my $c0 = "r10";
my $bp0 = "r11";
my $bpi = "r11";
@@ -188,7 +186,6 @@ sub mul_mont_fixed($)
.globl .${fname}
.align 5
.${fname}:
- mr $rp,r3
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