riscv64: fix mips-ism.

r29 is the stack pointer on mips, but it's x2 on riscv64 (and the git
history shows that this was indeed copy & pasted from the mips code)
and since bionic always sets up a signal stack with sigaltstack() I
doubt the comment was relevant even on mips (but no-one ever used it,
so who'd know?).

While I'm here, stop using decimal arithmetic --- the whole point was to
have each register contain the value that was obviously appropriate for
that register. (riscv64's mips-like mess of registers all over the place
means that's not going to be super readable, but there's no reason to
make it worse.)

Also, even though I personally prefer the 0xdead from the old mips code,
everyone else is using 0xa5a5, so let's make riscv64 match the others.

Test: treehugger
Change-Id: Ibbae821bc0a02e07164147d621e342224528c2c9
diff --git a/debuggerd/crasher/riscv64/crashglue.S b/debuggerd/crasher/riscv64/crashglue.S
index 5334887..42f59b3 100644
--- a/debuggerd/crasher/riscv64/crashglue.S
+++ b/debuggerd/crasher/riscv64/crashglue.S
@@ -6,39 +6,38 @@
 	sd ra, 8(sp)
 	.cfi_offset ra, -8
 
-	li	x0,0xdead0000+0
-	li	x1,0xdead0000+1
-	li	x2,0xdead0000+2
-	li	x3,0xdead0000+3
-	li	x4,0xdead0000+4
-	li	x5,0xdead0000+5
-	li	x6,0xdead0000+6
-	li	x7,0xdead0000+7
-	li	x8,0xdead0000+8
-	li	x9,0xdead0000+9
-	li	x10,0xdead0000+10
-	li	x11,0xdead0000+11
-	li	x12,0xdead0000+12
-	li	x13,0xdead0000+13
-	li	x14,0xdead0000+14
-	li	x15,0xdead0000+15
-	li	x16,0xdead0000+16
-	li	x17,0xdead0000+17
-	li	x18,0xdead0000+18
-	li	x19,0xdead0000+19
-	li	x20,0xdead0000+20
-	li	x21,0xdead0000+21
-	li	x22,0xdead0000+22
-	li	x23,0xdead0000+23
-	li	x24,0xdead0000+24
-	li	x25,0xdead0000+25
-	li	x26,0xdead0000+26
-	li	x27,0xdead0000+27
-	li	x28,0xdead0000+28
-	# don't trash the stack otherwise the signal handler won't run
-	#li	x29,0xdead0000+29
-	li	x30,0xdead0000+30
-	li	x31,0xdead0000+31
+	li	x0,0xa5a50000
+	li	x1,0xa5a50001
+	li	x2,0xa5a50002
+	li	x3,0xa5a50003
+	li	x4,0xa5a50004
+	li	x5,0xa5a50005
+	li	x6,0xa5a50006
+	li	x7,0xa5a50007
+	li	x8,0xa5a50008
+	li	x9,0xa5a50009
+	li	x10,0xa5a50010
+	li	x11,0xa5a50011
+	li	x12,0xa5a50012
+	li	x13,0xa5a50013
+	li	x14,0xa5a50014
+	li	x15,0xa5a50015
+	li	x16,0xa5a50016
+	li	x17,0xa5a50017
+	li	x18,0xa5a50018
+	li	x19,0xa5a50019
+	li	x20,0xa5a50020
+	li	x21,0xa5a50021
+	li	x22,0xa5a50022
+	li	x23,0xa5a50023
+	li	x24,0xa5a50024
+	li	x25,0xa5a50025
+	li	x26,0xa5a50026
+	li	x27,0xa5a50027
+	li	x28,0xa5a50028
+	li	x29,0xa5a50029
+	li	x30,0xa5a50030
+	li	x31,0xa5a50031
 
 	li sp, 0
 	ld t2, 0(zero)