The entire flash chip S25FS512S consists of uniform 256KB sectors.
Additionally, it has three configurations:
* 0x01: Eight 4KB sectors (32KB in total) overlaying the start of
the first 256KB sector
* 0x03: Eight 4KB sectors (32KB in total) overlaying the end of the
last 256KB sector
* 0x05: No overlaying sectors

The active configuration is determined from bit fields of two
registers, CR1NV and CR3NV.

Mbed OS does not currently support partially overlaying sectors,
meaning that with eight 4KB sectors overlay a 256KB sectors, the
remaining 224KB (== 256KB - 8 * 4KB) of the big sector can't be
correctly handled. Supporting such scenario would involve a large
amount of rewriting in Mbed OS's BlockDevice, SFDP and their tests,
and may increase the code size.

So, this commit applies a quirk to always report configuration 0x05
(no overlaying sectors). Even if 0x01 or 0x03 is the real configuration,
they are compatible with the 0x05 configuration because 256KB sectors
exist in all cases.

Note: This quirk does *not* change actual configurations on hardware,
because registers CR1NV and CR3NV are one-time configurable (OTP) -
each bit field has a factory value of 0 and can be changed to 1 by the
user but not back to 0. So QSPIFBlockDevice avoids changing them.