gdb: xtensa: fix register counters for xtensa-linux

gdb: xtensa: fix register counters for xtensa-linux

Commit 37d9e0623102 ("gdb: xtensa: handle privileged registers") changed
how the tdep->num_regs and tdep->num_pseudo_regs are calculated, but
didn't update these numbers in the gdbarch for the xtensa-linux target.
As a result xtensa-linux-gdb behaves as xtensa-elf-gdb and cannot
communicate with the linux gdbserver.
Fix tdep->num_pseudo_regs calculation and call set_gdbarch_num_regs and
set_gdbarch_num_pseudo_regs in xtensa_linux_init_abi.

gdb/
2019-01-13  Max Filippov  <jcmvbkbc@gmail.com>

	* xtensa-linux-tdep.c (xtensa_linux_init_abi): Update
	tdep->num_pseudo_regs. Add calls to set_gdbarch_num_regs and
	set_gdbarch_num_pseudo_regs.