Integrate 5.x SMC API changes, add 4.x specific setup, implement target firmware selection

Fix off-by-one mkey revision errors

Fix async expMod output + smcUnwrapAesWrappedTitlekey

Fix smcComputeCmac, generally improve userpage cache usage

memcpy(x, NULL, 0) is undefined behavior

Fix and with mask issue in smc_user.c

Fix user_generate_specific_aes_key wrong register use

Fix bug in user_generate_specific_aes_key, add other read/write le/be funcs

Rename cache.s/.h to arm.s/.h

Move source files to src/, add Makefile, fix all build and linkage errors, etc.