spi: stm32-qspi: flags management fixes

Merge series from patrice.chotard@foss.st.com <patrice.chotard@foss.st.com>
Patrice Chotard <patrice.chotard@foss.st.com>:

From: Patrice Chotard <patrice.chotard@foss.st.com>

This series update flags management in the following cases:
  - In APM mode, don't take care of TCF and TEF flags
  - Always check TCF flag in stm32_qspi_wait_cmd()
  - Don't check BUSY flag when sending new command