mtd: nand/fsmc: Use devm routines

fsmc_nand driver currently uses normal kzalloc, request_mem etc routines. This
patch replaces these routines with devm_kzalloc and devm_request_mem_region etc.
Consequently, the error and driver removal scenarios are curtailed.

Signed-off-by: Vipin Kumar <vipin.kumar@st.com>
Reviewed-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>