mtd: tests: annotate as DANGEROUS in Kconfig
mtd: tests: annotate as DANGEROUS in Kconfig

The tests may erase mtd devices, so annotate them as suggested per
coding style and add a paragraph to the help text as well.

Artem: amended the help test a bit.

Signed-off-by: Wolfram Sang <3883f8aab0424a154a3bcb43ff874b819786efbe@pengutronix.de>
Signed-off-by: Artem Bityutskiy <19b5733dcea388885746d36043d3568bba5b4df7@intel.com>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs