When I am not mistaken, the easiest way to solve it is by moving the y_axis text to the (sub) title area of the plot. Here is an example. Adjust hjust to a value that suit your needs (I could not check the range myself owing to limitations of my mobile)
library(ggplot2)
ggplot(mtcars, aes(x=hp, y=mpg)) + geom_point() +
ggtitle("mpg") +
theme(
axis.title.y = element_blank(),
plot.title = element_text(hjust=0))
Hope this helps,
JW