media: c8sectpfe: Use resource_size function on memory resource

To adapt fei->sram_size calculation via resource_size for memory size
calculation before, in fei->sram = devm_ioremap_resource(dev, res).
And make memory initialization range in
memset_io for fei->sram appropriate

Signed-off-by: Vasyl Gomonovych <gomonovych@gmail.com>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>