Rtcmem update

[mcspr]

• remove rtcmem.test command that was doing nothing
• replace memset with direct address writes. adds a debug with start/end address
• nicer rtcmem.dump. prints all usable block instead of just the ones used. still show the number of continuous blocks used in the status string at the top:

[080089] [RTCMEM] boot_status=0 status=0 blocks_used=8
[080090] 00 60001280: 00000000 00000001 00000002 00000003 00000004 00000005 00000006 00000007
[080091] 08 600012a0: 00000008 00000009 0000000a 0000000b 0000000c 0000000d 0000000e 0000000f
[080100] 16 600012c0: 00000010 00000011 00000012 00000013 00000014 00000015 00000016 00000017
[080109] 24 600012e0: 00000018 00000019 0000001a 0000001b 0000001c 0000001d 0000001e 0000001f
[080118] 32 60001300: 00000020 00000021 00000022 00000023 00000024 00000025 00000026 00000027
[080127] 40 60001320: 00000028 00000029 0000002a 0000002b 0000002c 0000002d 0000002e 0000002f
[080136] 48 60001340: 00000030 00000031 00000032 00000033 00000034 00000035 00000036 00000037
[080145] 56 60001360: 00000038 00000039 0000003a 0000003b 0000003c 0000003d 0000003e 0000003f
[080154] 64 60001380: 00000040 00000041 00000042 00000043 00000044 00000045 00000046 00000047
[080163] 72 600013a0: 00000048 00000049 0000004a 0000004b 0000004c 0000004d 0000004e 0000004f
[080172] 80 600013c0: 00000050 00000051 00000052 00000053 00000054 00000055 00000056 00000057
[080181] 88 600013e0: 00000058 00000059 0000005a 0000005b 0000005c 0000005d 0000005e 0000005f