cfi_flash: don't hide write/erase errors

Partially revert commit 0d01f66d235118 (CFI: cfi_flash write fix for AMD
legacy).

flash_full_status_check() used to skip status register parsing when
flash_status_check() returns OK. This is wrong since flash_status_check()
must return OK for other status bits to be valid.

Cc: Ed Swarthout <Ed.Swarthout@freescale.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Stefan Roese <sr@denx.de>