Added -mcpu option for assembling .s files (fixes deprecated mcr instruction warnings)



git-svn-id: file:///var/johncronin-svn/rpi-boot@54 0f3ef04d-8e58-4d2a-b558-b31704943fbb
Changed uart.c to use usleep() instead of inline asm delay function



git-svn-id: file:///var/johncronin-svn/rpi-boot@55 0f3ef04d-8e58-4d2a-b558-b31704943fbb