Edit QuadSPI.md

Fix minor branding nit.

Author: Amanda Butler

docs/api/drivers/QuadSPI.md

@@ -22,7 +22,7 @@ For more information, please review the related content.
 
 ### Related content
 
-- [Quad-SPI flash block device](https://github.com/ARMmbed/qspif-blockdevice).
+- [QSPI flash block device](https://github.com/ARMmbed/qspif-blockdevice).
 - [STMicroelectronics Quad-SPI documentation](https://www.st.com/content/ccc/resource/technical/document/application_note/group0/b0/7e/46/a8/5e/c1/48/01/DM00227538/files/DM00227538.pdf/jcr:content/translations/en.DM00227538.pdf).
 - [Macronix MX25R6435F flash memory with Quad-SPI](http://www.macronix.com/Lists/Datasheet/Attachments/6270/MX25R6435F,%20Wide%20Range,%2064Mb,%20v1.4.pdf).
 - [Nordic Quad-SPI support in NRF52840](http://infocenter.nordicsemi.com/pdf/nRF52840_OPS_v0.5.pdf).