Fix register mapping to avoid volatile registers and issues with R12
Fix register mapping to avoid volatile registers and issues with R12

Signed-off-by: Alan Jowett <7adadd5b1a96ae3ed1701c18268cba2dc82c7275@microsoft.com>

iovisor/ubpf,iovisor/ubpf,iovisor/ubpf,iovisor/ubpf