powerpc: fix 8xx and 82xx type-punning warnings with GCC 4.7

C99's strict aliasing rules are insane to use in low-level code such as a
bootloader, but as Wolfgang has rejected -fno-strict-aliasing in the
past, add a union so that 16-bit accesses can be performed.

Compile-tested only.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Acked-by: Wolfgang Denk <wd@denx.de>
ppc: ppmc7xx: Fix possible out-of-bound access

The flash_info_t->start[] field is limited in size by CONFIG_SYS_MAX_FLASH_SECT
macro, which is set to 19 for this board in the board config file. If we inspect
the board/ppmc7xx/flash.c closely, especially the flash_get_size() function, we
can notice the "switch ((long)flashtest)" at around line 80 having a few results
which will set flash_info_t->sector_count to value higher than 19, for example
"case AMD_ID_LV640U" will set it to 128. Notice that right underneath, iteration
over flash_info_t->start[] happens and the upper bound for the interation is
flash_info_t->sector_count. Now if the sector_count is 128 as it is for the
AMD_ID_LV640U case, but the CONFIG_SYS_MAX_FLASH_SECT limiting the start[] is
only 19, an access past the start[] array much happen. Moreover, during this
iteration, the field is written to, so memory corruption is inevitable.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Tom Rini <trini@ti.com>
Cc: Richard Danter <richard.danter@windriver.com>
Merge branch 'master' of git://git.denx.de/u-boot-74xx-7xx