drivers: misc: sram: fix up some const issues with recent attribute changes

The binary attribute const changes recently for the sram driver were
made in a way that hid the fact that we would be casting a const pointer
to a non-const one.  So explicitly make the cast so that it is obvious
and preserve the const pointer in the sram_reserve_cmp() function.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Fixes: c3b8c358 ("misc: sram: constify 'struct bin_attribute'")
Link: https://lore.kernel.org/r/2025052125-squid-sandstorm-a418@gregkh


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>