edac: llcc: Add NULL pointer check and fix data types

Add NULL pointer check to make sure edac device is allocated properly,
pass nr_blocks as 0 to edac alloc control device api since the
block_name is null in case of llcc and change the data type of
llcc_banks to u32 instead of phys_addr_t.

Change-Id: I52a0d33a0d546db235751104cd225c29f79f5356
Signed-off-by: Channagoud Kadabi <ckadabi@codeaurora.org>