[gdb/testsuite] Fix cur_addr update in gdb.base/watchpoint-reuse-slot.exp

I noticed this code in gdb.base/watchpoint-reuse-slot.exp, proc stepi:
...
    gdb_test_multiple "stepi" $test {
	-re "($hex).*[string_to_regexp $srcline]\r\n$gdb_prompt $" {
	    set addr $expect_out(1,string)
	    if {$addr != $cur_addr} {
		pass $test
	    } else {
		fail $test
	    }
	    set cur_addr addr
	}
    }
...

The variable cur_addr is documented as:
...
 # The address the program is stopped at currently.
 set cur_addr ""
...
but in the gdb_test_multiple clause we assign the string "addr" to cur_addr,
while $addr contains the current address.

Fix this by assigning $addr instead "addr".

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2020-05-06  Tom de Vries  <tdevries@suse.de>

	* gdb.base/watchpoint-reuse-slot.exp: Fix incorrect assignment.

2 files changed, 5 insertions, 1 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 7a62fe8ce77..fde713527d6 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 2020-05-06  Tom de Vries  <tdevries@suse.de>
 
+	* gdb.base/watchpoint-reuse-slot.exp: Fix incorrect assignment.
+
+2020-05-06  Tom de Vries  <tdevries@suse.de>
+
 	* gdb.base/store.exp (check_set, up_set): Allowing missing location
 	info for r.
 
diff --git a/gdb/testsuite/gdb.base/watchpoint-reuse-slot.exp b/gdb/testsuite/gdb.base/watchpoint-reuse-slot.exp
index 73213787c61..83b970380ca 100644
--- a/gdb/testsuite/gdb.base/watchpoint-reuse-slot.exp
+++ b/gdb/testsuite/gdb.base/watchpoint-reuse-slot.exp
@@ -73,7 +73,7 @@ proc stepi {} {
 	    } else {
 		fail $test
 	    }
-	    set cur_addr addr
+	    set cur_addr $addr
 	}
     }
 }