ARM: 6291/1: coresight: move struct tracectx inside etm driver

This is done so as to be able to make use of the coresight components'
registers in assembler code (like omap sleep code). Also, there shouldn't
be any users of this structure outside the etm driver.

Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Alexander Shishkin <virtuoso@slind.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>