[gdb] Fix typos in comments

[gdb] Fix typos in comments

Fix typos in comments.  NFC.

Tested on x86_64-linux.

gdb/ChangeLog:

2019-10-17  Tom de Vries  <tdevries@suse.de>

	* arm-nbsd-nat.c: Fix typos in comments.
	* arm-tdep.c: Same.
	* darwin-nat-info.c: Same.
	* dwarf2read.c: Same.
	* elfread.c: Same.
	* event-top.c: Same.
	* findvar.c: Same.
	* gdbtypes.c: Same.
	* hppa-tdep.c: Same.
	* i386-tdep.c: Same.
	* jit.c: Same.
	* main.c: Same.
	* mdebugread.c: Same.
	* moxie-tdep.c: Same.
	* nto-procfs.c: Same.
	* osabi.c: Same.
	* ppc-linux-tdep.c: Same.
	* remote.c: Same.
	* riscv-tdep.c: Same.
	* s390-tdep.c: Same.
	* sh-tdep.c: Same.
	* sparc-linux-tdep.c: Same.
	* sparc-nat.c: Same.
	* stack.c: Same.
	* target-descriptions.c: Same.
	* top.c: Same.
	* varobj.c: Same.

Change-Id: I6047967abd2d51c9000dea15184d19f4e952c3ff