[armel] Change size limit of armel kernel image back to 2097080

Reduce armel image size by:
- Set CONFIG_CRYPTO_MANAGER_DISABLE_TESTS=y
- Change MTD, MTD_CMDLINE_PARTS, RTC_DRV_MV, and SPI_ORION from
  built-in to module.
- Disable VT, ZSWAP, RD_BZIP2, and RD_LZMA.

So qnap support is back.

Thanks to Leigh Brown <leigh@solinno.co.uk> for his idea to disable VT.

(cherry picked from commit a4fdfa09)