imx8mm-cl-iot-gate: Retrieve the DDR type from EEPROM

imx8mm-cl-iot-gate: Retrieve the DDR type from EEPROM

Currently, the DDR type is retrieved by iteracting inside an array
of possible DDR types.

This may take saveral attempts, which slows the overall U-Boot process
and does not provide a good user experience:

U-Boot SPL 2021.07 (Feb 28 2022 - 06:39:32 +0000)
DDRINFO: Cfg attempt: [ 1/6 ]
DDRINFO(M): mr5-8 [ 0xff000010 ]
DDRINFO(T): mr5-8 [ 0x5000010 ]
resetting ...

U-Boot SPL 2021.07 (Feb 28 2022 - 06:39:32 +0000)
DDRINFO: Cfg attempt: [ 2/6 ]
DDRINFO(M): mr5-8 [ 0xff000010 ]
DDRINFO(T): mr5-8 [ 0x1061010 ]
resetting ...

U-Boot SPL 2021.07 (Feb 28 2022 - 06:39:32 +0000)
DDRINFO: Cfg attempt: [ 3/6 ]
DDRINFO(M): mr5-8 [ 0xff000010 ]
DDRINFO(T): mr5-8 [ 0xff000010 ]
Normal Boot
WDT:   Not starting
Trying to boot from MMC2
NOTICE:  BL31: v2.5(release):v2.5
NOTICE:  BL31: Built : 07:12:44, Jan 24 2022

Improve the boot time by retrieving the correct DDR information from
the EEPROM:

U-Boot SPL 2022.04-rc4-00045-g6d02bc40d58c (Mar 19 2022 - 08:22:29 -0300)
DDRINFO(D): Kingston 4096G
DDRINFO(M): mr5-8 [ 0xff000010 ]
DDRINFO(E): mr5-8 [ 0xff000010 ]
Normal Boot
WDT:   Started watchdog@30280000 with servicing (60s timeout)
Trying to boot from MMC2
NOTICE:  BL31: v2.5(release):v2.5
NOTICE:  BL31: Built : 22:28:11, Mar 15 2022

Based on the original code from Compulab's U-Boot.

Tested on a imx8mm-cl-iot-gate board populated with 4GB of RAM.

Signed-off-by: Fabio Estevam <festevam@denx.de>