arm: mach-keystone: Fixes issue with return values in inline assembly

arm: mach-keystone: Fixes issue with return values in inline assembly

The inline assembly functions in mon.c assume that the caller will
check for the return value in r0 according to regular ARM calling
conventions.

However, this assumption breaks down if the compiler inlines the
functions. The caller is then under no obligation to use r0 for the
result.

To fix this disconnect, we must explicitly move the return value
from the smc/bl call to the variable that the function returns.

Signed-off-by: Madan Srinivas <madans@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>