[gdb/testsuite] allow more registers in gdb.base/jit-reader.exp

[gdb/testsuite] allow more registers in gdb.base/jit-reader.exp

Fixes jit-reader test failures on systems that have more registers than
expected by the current condition.

On Intel i9-7920X the following extra registers are printed:

k0             0x0                 0
k1             0x0                 0
k2             0x0                 0
k3             0x0                 0
k4             0x0                 0
k5             0x0                 0
k6             0x0                 0
k7             0x0                 0

gdb/testsuite/ChangeLog:

2020-02-18  Mihails Strasuns  <mihails.strasuns@intel.com>

	* gdb.base/jit-reader.exp: Relax register output check.