Fix for build issue on i386.xen and amd64.xen.

This is a duplicate variable reference in mrsas, so now this patch isolate atomic_ variable and relavent
function call using prefix mrsas_xx.

Issue was introduced in r272737.

MFC after:	2 weeks
Sponsored by:	Avago Technology
Start removing the omap3 support. In base it was only ever a header and a
few changes to drivers, no kernel config was added. As the SoCs are quite
old and the code is unmaintained start the process of removing support by
deleting the header file and code that depends on it along with the macro
SOC_OMAP3. Other Ti SoCs shouldn't be affected, other than for us to have
less code to maintain.

Differential Revision:	https://reviews.freebsd.org/D936
Reviewed by:	rpaulo, loos