package/musl: bump to version 1.2.0

package/musl: bump to version 1.2.0

Also:
 * Drop patch 0003 which is included in the new version.
 * Update hash value of the COPYRIGHT file as the copyright year was
   updated.

>From the release history [1]:

This release moves all 32-bit archs to 64-bit time_t, enabling them
to represent times beyond January of 2038.

There are no new requirements on kernel version, and this is not a
hard ABI break, but the type changes do impact compatibility between
code built against previous versions of musl and code built against
musl 1.2. Users upgrading 32-bit systems should read the detailed
time64 release notes [2]. 64-bit systems are not affected.

In addition, character data has been updated to align with Unicode
12.1.0, along with fixes for some errors in the data and a replacement
for inefficient and unmaintainable case-mapping code. Correctness of
results has been improved in the math library, particularly some complex
functions and 32-bit x86 asm. Various arch-specific bugs have also been
fixed.

[1] https://musl.libc.org/releases.html
[2] https://musl.libc.org/time64.html

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>