Flash memory size not aligned to address

Flash memory size not aligned to address

(This patch is from Mark Rages <markrages@gmail.com>.)

The Nordic nRF52 memory map, reported from black magic probe:

Num Enb Low Addr High Addr Attrs
0 y 0x00000000 0x00080000 flash blocksize 0x1000 nocache
1 y 0x10001000 0x10001210 flash blocksize 0x210 nocache
2 y 0x20000000 0x20010000 rw nocache

The region at 0x10001000 is "UICR" and it is a section of flash that is
erased all at once.

Notice the odd size: 0x210 is the size of the region defined in the
datasheet.

But because the block size was listed as 0x210, gdb was insisting on
issuing two erase commands divisible by 0x210, starting below 0x10001000.

This patch fixes it by doing the alignment computation from the start of
the region, not from address 0.

gdb/ChangeLog:

	* target-memory.c (block_boundaries): Fix for block address not
	aligned on block size.